import {
    AnimationClip,
    Bone,
    Box3,
    BufferAttribute,
    BufferGeometry,
    ClampToEdgeWrapping,
    Color,
    DirectionalLight,
    DoubleSide,
    FrontSide,
    Group,
    InstancedMesh,
    InterleavedBuffer,
    InterleavedBufferAttribute,
    Interpolant,
    InterpolateDiscrete,
    InterpolateLinear,
    Line,
    LineBasicMaterial,
    LineLoop,
    LineSegments,
    LinearFilter,
    LinearMipmapLinearFilter,
    LinearMipmapNearestFilter,
    Loader,
    LoaderUtils,
    Material,
    MathUtils,
    Matrix4,
    Mesh,
    MeshBasicMaterial,
    MeshPhysicalMaterial,
    MeshStandardMaterial,
    MirroredRepeatWrapping,
    NearestFilter,
    NearestMipmapLinearFilter,
    NearestMipmapNearestFilter,
    NumberKeyframeTrack,
    Object3D,
    OrthographicCamera,
    PerspectiveCamera,
    PointLight,
    Points,
    PointsMaterial,
    PropertyBinding,
    Quaternion,
    QuaternionKeyframeTrack,
    RepeatWrapping,
    Skeleton,
    SkinnedMesh,
    Sphere,
    SpotLight,
    Texture,
    TriangleFanDrawMode,
    TriangleStripDrawMode,
    Vector2,
    Vector3,
    VectorKeyframeTrack,
    sRGBEncoding,
    LoadingManager,
    Camera
} from 'three';
import { MeshoptDecoder } from '../libs/meshopt_decoder.module';
import { toTrianglesDrawMode } from '../utils/buffer_geometry_utils';
import { XHRResponseType } from '../xhr/xhr_request';
import { DRACOLoader } from './draco_loader';
import { FileLoader } from './file_loader';
import { ImageBitmapLoader } from './imagebitmap_loader';
import { KTX2Loader } from './ktx2_loader';
import { TextureLoader } from './texture_loader';


type PluginCallback = (parser: any) => any;

type GLTF = any;

type OnLoad = (gltf: GLTF) => void;
type OnProgress = (total: number, loaded: number) => void;
type OnError = (err: any) => void;

export class GLTFLoader extends Loader {

    public dracoLoader?: DRACOLoader = null;
    public ktx2Loader?: KTX2Loader = null;
    public meshoptDecoder?: any = null;

    public pluginCallbacks: PluginCallback[] = [];

    public constructor (manager?: LoadingManager) {

        super(manager);

        this.setMeshoptDecoder(MeshoptDecoder);

        this.register(function (parser) {

            return new GLTFMaterialsClearcoatExtension(parser);

        });

        this.register(function (parser) {

            return new GLTFTextureBasisUExtension(parser);

        });

        this.register(function (parser) {

            return new GLTFTextureWebPExtension(parser);

        });

        this.register(function (parser) {

            return new GLTFTextureAVIFExtension(parser);

        });

        this.register(function (parser) {

            return new GLTFMaterialsSheenExtension(parser);

        });

        this.register(function (parser) {

            return new GLTFMaterialsTransmissionExtension(parser);

        });

        this.register(function (parser) {

            return new GLTFMaterialsVolumeExtension(parser);

        });

        this.register(function (parser) {

            return new GLTFMaterialsIorExtension(parser);

        });

        this.register(function (parser) {

            return new GLTFMaterialsEmissiveStrengthExtension(parser);

        });

        this.register(function (parser) {

            return new GLTFMaterialsSpecularExtension(parser);

        });

        this.register(function (parser) {

            return new GLTFMaterialsIridescenceExtension(parser);

        });

        this.register(function (parser) {

            return new GLTFLightsExtension(parser);

        });

        this.register(function (parser) {

            return new GLTFMeshoptCompression(parser);

        });

        this.register(function (parser) {

            return new GLTFMeshGpuInstancing(parser);

        });

    }

    public load (url: string, onLoad?: OnLoad, onProgress?: OnProgress, onError?: OnError) {

        const scope = this;

        let resourcePath;

        if (this.resourcePath !== '') {

            resourcePath = this.resourcePath;

        } else if (this.path !== '') {

            resourcePath = this.path;

        } else {

            resourcePath = LoaderUtils.extractUrlBase(url);

        }

        // Tells the LoadingManager to track an extra item, which resolves after
        // the model is fully loaded. This means the count of items loaded will
        // be incorrect, but ensures manager.onLoad() does not fire early.
        this.manager.itemStart(url);

        const _onError = function (e) {

            if (onError) {

                onError(e);

            } else {

                console.error(e);

            }

            scope.manager.itemError(url);
            scope.manager.itemEnd(url);

        };

        const loader = new FileLoader(this.manager);

        loader.setPath(this.path);
        loader.setResponseType(XHRResponseType.ARRAYBUFFER);
        loader.setRequestHeader(this.requestHeader);
        loader.setWithCredentials(this.withCredentials);
        loader.setLoadInWorker(true);

        loader.load(url, function (data: ArrayBuffer) {

            try {

                scope.parse(data, resourcePath, function (gltf) {

                    onLoad(gltf);

                    scope.manager.itemEnd(url);

                }, _onError);

            } catch (e) {

                _onError(e);

            }

        }, onProgress, _onError);

    }

    public setDRACOLoader (dracoLoader: DRACOLoader) {

        this.dracoLoader = dracoLoader;
        return this;

    }

    public setDDSLoader () {

        throw new Error(

            'THREE.GLTFLoader: "MSFT_texture_dds" no longer supported. Please update to "KHR_texture_basisu".'

        );

    }

    public setKTX2Loader (ktx2Loader: KTX2Loader) {

        this.ktx2Loader = ktx2Loader;
        return this;

    }

    public setMeshoptDecoder (meshoptDecoder: any) {

        this.meshoptDecoder = meshoptDecoder;
        return this;

    }

    public register (callback: PluginCallback) {

        if (this.pluginCallbacks.indexOf(callback) === - 1) {

            this.pluginCallbacks.push(callback);

        }

        return this;

    }

    public unregister (callback: PluginCallback) {

        if (this.pluginCallbacks.indexOf(callback) !== - 1) {

            this.pluginCallbacks.splice(this.pluginCallbacks.indexOf(callback), 1);

        }

        return this;

    }

    public parse (data: ArrayBuffer | string, path: string, onLoad?: OnLoad, onError?: OnError) {

        let json;
        const extensions = {};
        const plugins = {};
        const textDecoder = new TextDecoder();

        if (typeof data === 'string') {

            json = JSON.parse(data);

        } else if (data instanceof ArrayBuffer) {

            const magic = textDecoder.decode(new Uint8Array(data, 0, 4));

            if (magic === BINARY_EXTENSION_HEADER_MAGIC) {

                try {

                    extensions[EXTENSIONS.KHR_BINARY_GLTF] = new GLTFBinaryExtension(data);

                } catch (error) {

                    if (onError) onError(error);
                    return;

                }

                json = JSON.parse(extensions[EXTENSIONS.KHR_BINARY_GLTF].content);

            } else {

                json = JSON.parse(textDecoder.decode(data));

            }

        } else {

            json = data;

        }

        if (json.asset === undefined || json.asset.version[0] < 2) {

            if (onError) onError(new Error('THREE.GLTFLoader: Unsupported asset. glTF versions >=2.0 are supported.'));
            return;

        }

        const parser = new GLTFParser(json, {

            path: path || this.resourcePath || '',
            crossOrigin: this.crossOrigin,
            requestHeader: this.requestHeader,
            manager: this.manager,
            ktx2Loader: this.ktx2Loader,
            meshoptDecoder: this.meshoptDecoder

        });

        parser.fileLoader.setRequestHeader(this.requestHeader);

        for (let i = 0; i < this.pluginCallbacks.length; i++) {

            const plugin = this.pluginCallbacks[i](parser);
            plugins[plugin.name] = plugin;

            // Workaround to avoid determining as unknown extension
            // in addUnknownExtensionsToUserData().
            // Remove this workaround if we move all the existing
            // extension handlers to plugin system
            extensions[plugin.name] = true;

        }

        if (json.extensionsUsed) {

            for (let i = 0; i < json.extensionsUsed.length; ++i) {

                const extensionName = json.extensionsUsed[i];
                const extensionsRequired = json.extensionsRequired || [];

                switch (extensionName) {

                    case EXTENSIONS.KHR_MATERIALS_UNLIT:
                        extensions[extensionName] = new GLTFMaterialsUnlitExtension();
                        break;

                    case EXTENSIONS.KHR_DRACO_MESH_COMPRESSION:
                        extensions[extensionName] = new GLTFDracoMeshCompressionExtension(json, this.dracoLoader);
                        break;

                    case EXTENSIONS.KHR_TEXTURE_TRANSFORM:
                        extensions[extensionName] = new GLTFTextureTransformExtension();
                        break;

                    case EXTENSIONS.KHR_MESH_QUANTIZATION:
                        extensions[extensionName] = new GLTFMeshQuantizationExtension();
                        break;

                    default:

                        if (extensionsRequired.indexOf(extensionName) >= 0 && plugins[extensionName] === undefined) {

                            console.warn('THREE.GLTFLoader: Unknown extension "' + extensionName + '".');

                        }

                }

            }

        }

        parser.setExtensions(extensions);
        parser.setPlugins(plugins);
        parser.parse(onLoad, onError);

    }

    parseAsync (data, path) {

        const scope = this;

        return new Promise(function (resolve, reject) {

            scope.parse(data, path, resolve, reject);

        });

    }

}

/* GLTFREGISTRY */

class GLTFRegistry {

    private objects = {};

    get (key) {

        return this.objects[key];

    }

    add (key, object) {

        this.objects[key] = object;

    }

    remove (key) {

        delete this.objects[key];

    }

    removeAll () {

        this.objects = {};

    }

}

/*********************************/
/********** EXTENSIONS ***********/
/*********************************/

const EXTENSIONS = {
    KHR_BINARY_GLTF: 'KHR_binary_glTF',
    KHR_DRACO_MESH_COMPRESSION: 'KHR_draco_mesh_compression',
    KHR_LIGHTS_PUNCTUAL: 'KHR_lights_punctual',
    KHR_MATERIALS_CLEARCOAT: 'KHR_materials_clearcoat',
    KHR_MATERIALS_IOR: 'KHR_materials_ior',
    KHR_MATERIALS_SHEEN: 'KHR_materials_sheen',
    KHR_MATERIALS_SPECULAR: 'KHR_materials_specular',
    KHR_MATERIALS_TRANSMISSION: 'KHR_materials_transmission',
    KHR_MATERIALS_IRIDESCENCE: 'KHR_materials_iridescence',
    KHR_MATERIALS_UNLIT: 'KHR_materials_unlit',
    KHR_MATERIALS_VOLUME: 'KHR_materials_volume',
    KHR_TEXTURE_BASISU: 'KHR_texture_basisu',
    KHR_TEXTURE_TRANSFORM: 'KHR_texture_transform',
    KHR_MESH_QUANTIZATION: 'KHR_mesh_quantization',
    KHR_MATERIALS_EMISSIVE_STRENGTH: 'KHR_materials_emissive_strength',
    EXT_TEXTURE_WEBP: 'EXT_texture_webp',
    EXT_TEXTURE_AVIF: 'EXT_texture_avif',
    EXT_MESHOPT_COMPRESSION: 'EXT_meshopt_compression',
    EXT_MESH_GPU_INSTANCING: 'EXT_mesh_gpu_instancing'
};

/**
 * Punctual Lights Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_lights_punctual
 */
class GLTFLightsExtension {

    public name = EXTENSIONS.KHR_LIGHTS_PUNCTUAL;

    public parser: GLTFParser;

    // Object3D instance caches
    public cache = { refs: {}, uses: {} };

    constructor (parser: GLTFParser) {

        this.parser = parser;
    }

    _markDefs () {

        const parser = this.parser;
        const nodeDefs = this.parser.json.nodes || [];

        for (let nodeIndex = 0, nodeLength = nodeDefs.length; nodeIndex < nodeLength; nodeIndex++) {

            const nodeDef = nodeDefs[nodeIndex];

            if (nodeDef.extensions
                && nodeDef.extensions[this.name]
                && nodeDef.extensions[this.name].light !== undefined) {
                //@ts-ignore
                parser._addNodeRef(this.cache, nodeDef.extensions[this.name].light);

            }

        }

    }

    _loadLight (lightIndex) {

        const parser = this.parser;
        const cacheKey = 'light:' + lightIndex;
        let dependency = parser.cache.get(cacheKey);

        if (dependency) return dependency;

        const json = parser.json;
        const extensions = (json.extensions && json.extensions[this.name]) || {};
        const lightDefs = extensions.lights || [];
        const lightDef = lightDefs[lightIndex];
        let lightNode;

        const color = new Color(0xffffff);

        if (lightDef.color !== undefined) color.fromArray(lightDef.color);

        const range = lightDef.range !== undefined ? lightDef.range : 0;

        switch (lightDef.type) {

            case 'directional':
                lightNode = new DirectionalLight(color);
                lightNode.target.position.set(0, 0, - 1);
                lightNode.add(lightNode.target);
                break;

            case 'point':
                lightNode = new PointLight(color);
                lightNode.distance = range;
                break;

            case 'spot':
                lightNode = new SpotLight(color);
                lightNode.distance = range;
                // Handle spotlight properties.
                lightDef.spot = lightDef.spot || {};
                lightDef.spot.innerConeAngle = lightDef.spot.innerConeAngle !== undefined ? lightDef.spot.innerConeAngle : 0;
                lightDef.spot.outerConeAngle = lightDef.spot.outerConeAngle !== undefined ? lightDef.spot.outerConeAngle : Math.PI / 4.0;
                lightNode.angle = lightDef.spot.outerConeAngle;
                lightNode.penumbra = 1.0 - lightDef.spot.innerConeAngle / lightDef.spot.outerConeAngle;
                lightNode.target.position.set(0, 0, - 1);
                lightNode.add(lightNode.target);
                break;

            default:
                throw new Error('THREE.GLTFLoader: Unexpected light type: ' + lightDef.type);

        }

        // Some lights (e.g. spot) default to a position other than the origin. Reset the position
        // here, because node-level parsing will only override position if explicitly specified.
        lightNode.position.set(0, 0, 0);

        lightNode.decay = 2;

        assignExtrasToUserData(lightNode, lightDef);

        if (lightDef.intensity !== undefined) lightNode.intensity = lightDef.intensity;

        lightNode.name = parser.createUniqueName(lightDef.name || ('light_' + lightIndex));

        dependency = Promise.resolve(lightNode);

        parser.cache.add(cacheKey, dependency);

        return dependency;

    }

    getDependency (type, index) {

        if (type !== 'light') return;

        return this._loadLight(index);

    }

    createNodeAttachment (nodeIndex) {

        const self = this;
        const parser = this.parser;
        const json = parser.json;
        const nodeDef = json.nodes[nodeIndex];
        const lightDef = (nodeDef.extensions && nodeDef.extensions[this.name]) || {};
        const lightIndex = lightDef.light;

        if (lightIndex === undefined) return null;

        return this._loadLight(lightIndex).then(function (light) {
            //@ts-ignore
            return parser._getNodeRef(self.cache, lightIndex, light);

        });

    }

}

/**
 * Unlit Materials Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_unlit
 */
class GLTFMaterialsUnlitExtension {

    public name = EXTENSIONS.KHR_MATERIALS_UNLIT;

    constructor () {

    }

    getMaterialType () {

        return MeshBasicMaterial;

    }

    extendParams (materialParams, materialDef, parser) {

        const pending = [];

        materialParams.color = new Color(1.0, 1.0, 1.0);
        materialParams.opacity = 1.0;

        const metallicRoughness = materialDef.pbrMetallicRoughness;

        if (metallicRoughness) {

            if (Array.isArray(metallicRoughness.baseColorFactor)) {

                const array = metallicRoughness.baseColorFactor;

                materialParams.color.fromArray(array);
                materialParams.opacity = array[3];

            }

            if (metallicRoughness.baseColorTexture !== undefined) {

                pending.push(parser.assignTexture(materialParams, 'map', metallicRoughness.baseColorTexture, sRGBEncoding));

            }

        }

        return Promise.all(pending);

    }

}

/**
 * Materials Emissive Strength Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/blob/5768b3ce0ef32bc39cdf1bef10b948586635ead3/extensions/2.0/Khronos/KHR_materials_emissive_strength/README.md
 */
class GLTFMaterialsEmissiveStrengthExtension {

    public name = EXTENSIONS.KHR_MATERIALS_EMISSIVE_STRENGTH;

    public parser: GLTFParser;

    constructor (parser: GLTFParser) {

        this.parser = parser;

    }

    extendMaterialParams (materialIndex, materialParams) {

        const parser = this.parser;
        const materialDef = parser.json.materials[materialIndex];

        if (!materialDef.extensions || !materialDef.extensions[this.name]) {

            return Promise.resolve();

        }

        const emissiveStrength = materialDef.extensions[this.name].emissiveStrength;

        if (emissiveStrength !== undefined) {

            materialParams.emissiveIntensity = emissiveStrength;

        }

        return Promise.resolve();

    }

}

/**
 * Clearcoat Materials Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_clearcoat
 */
class GLTFMaterialsClearcoatExtension {

    public name = EXTENSIONS.KHR_MATERIALS_CLEARCOAT;

    public parser: GLTFParser;

    constructor (parser: GLTFParser) {

        this.parser = parser;

    }

    getMaterialType (materialIndex) {

        const parser = this.parser;
        const materialDef = parser.json.materials[materialIndex];

        if (!materialDef.extensions || !materialDef.extensions[this.name]) return null;

        return MeshPhysicalMaterial;

    }

    extendMaterialParams (materialIndex, materialParams) {

        const parser = this.parser;
        const materialDef = parser.json.materials[materialIndex];

        if (!materialDef.extensions || !materialDef.extensions[this.name]) {

            return Promise.resolve();

        }

        const pending = [];

        const extension = materialDef.extensions[this.name];

        if (extension.clearcoatFactor !== undefined) {

            materialParams.clearcoat = extension.clearcoatFactor;

        }

        if (extension.clearcoatTexture !== undefined) {

            pending.push(parser.assignTexture(materialParams, 'clearcoatMap', extension.clearcoatTexture));

        }

        if (extension.clearcoatRoughnessFactor !== undefined) {

            materialParams.clearcoatRoughness = extension.clearcoatRoughnessFactor;

        }

        if (extension.clearcoatRoughnessTexture !== undefined) {

            pending.push(parser.assignTexture(materialParams, 'clearcoatRoughnessMap', extension.clearcoatRoughnessTexture));

        }

        if (extension.clearcoatNormalTexture !== undefined) {

            pending.push(parser.assignTexture(materialParams, 'clearcoatNormalMap', extension.clearcoatNormalTexture));

            if (extension.clearcoatNormalTexture.scale !== undefined) {

                const scale = extension.clearcoatNormalTexture.scale;

                materialParams.clearcoatNormalScale = new Vector2(scale, scale);

            }

        }

        return Promise.all(pending);

    }

}

/**
 * Iridescence Materials Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_iridescence
 */
class GLTFMaterialsIridescenceExtension {

    public name = EXTENSIONS.KHR_MATERIALS_IRIDESCENCE;

    public parser: GLTFParser;

    constructor (parser: GLTFParser) {

        this.parser = parser;

    }

    getMaterialType (materialIndex) {

        const parser = this.parser;
        const materialDef = parser.json.materials[materialIndex];

        if (!materialDef.extensions || !materialDef.extensions[this.name]) return null;

        return MeshPhysicalMaterial;

    }

    extendMaterialParams (materialIndex, materialParams) {

        const parser = this.parser;
        const materialDef = parser.json.materials[materialIndex];

        if (!materialDef.extensions || !materialDef.extensions[this.name]) {

            return Promise.resolve();

        }

        const pending = [];

        const extension = materialDef.extensions[this.name];

        if (extension.iridescenceFactor !== undefined) {

            materialParams.iridescence = extension.iridescenceFactor;

        }

        if (extension.iridescenceTexture !== undefined) {

            pending.push(parser.assignTexture(materialParams, 'iridescenceMap', extension.iridescenceTexture));

        }

        if (extension.iridescenceIor !== undefined) {

            materialParams.iridescenceIOR = extension.iridescenceIor;

        }

        if (materialParams.iridescenceThicknessRange === undefined) {

            materialParams.iridescenceThicknessRange = [100, 400];

        }

        if (extension.iridescenceThicknessMinimum !== undefined) {

            materialParams.iridescenceThicknessRange[0] = extension.iridescenceThicknessMinimum;

        }

        if (extension.iridescenceThicknessMaximum !== undefined) {

            materialParams.iridescenceThicknessRange[1] = extension.iridescenceThicknessMaximum;

        }

        if (extension.iridescenceThicknessTexture !== undefined) {

            pending.push(parser.assignTexture(materialParams, 'iridescenceThicknessMap', extension.iridescenceThicknessTexture));

        }

        return Promise.all(pending);

    }

}

/**
 * Sheen Materials Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_materials_sheen
 */
class GLTFMaterialsSheenExtension {

    public name = EXTENSIONS.KHR_MATERIALS_SHEEN;

    public parser: GLTFParser;

    constructor (parser: GLTFParser) {

        this.parser = parser;

    }

    getMaterialType (materialIndex) {

        const parser = this.parser;
        const materialDef = parser.json.materials[materialIndex];

        if (!materialDef.extensions || !materialDef.extensions[this.name]) return null;

        return MeshPhysicalMaterial;

    }

    extendMaterialParams (materialIndex, materialParams) {

        const parser = this.parser;
        const materialDef = parser.json.materials[materialIndex];

        if (!materialDef.extensions || !materialDef.extensions[this.name]) {

            return Promise.resolve();

        }

        const pending = [];

        materialParams.sheenColor = new Color(0, 0, 0);
        materialParams.sheenRoughness = 0;
        materialParams.sheen = 1;

        const extension = materialDef.extensions[this.name];

        if (extension.sheenColorFactor !== undefined) {

            materialParams.sheenColor.fromArray(extension.sheenColorFactor);

        }

        if (extension.sheenRoughnessFactor !== undefined) {

            materialParams.sheenRoughness = extension.sheenRoughnessFactor;

        }

        if (extension.sheenColorTexture !== undefined) {

            pending.push(parser.assignTexture(materialParams, 'sheenColorMap', extension.sheenColorTexture, sRGBEncoding));

        }

        if (extension.sheenRoughnessTexture !== undefined) {

            pending.push(parser.assignTexture(materialParams, 'sheenRoughnessMap', extension.sheenRoughnessTexture));

        }

        return Promise.all(pending);

    }

}

/**
 * Transmission Materials Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_transmission
 * Draft: https://github.com/KhronosGroup/glTF/pull/1698
 */
class GLTFMaterialsTransmissionExtension {

    public name = EXTENSIONS.KHR_MATERIALS_TRANSMISSION;

    public parser: GLTFParser;

    constructor (parser: GLTFParser) {

        this.parser = parser;

    }

    getMaterialType (materialIndex) {

        const parser = this.parser;
        const materialDef = parser.json.materials[materialIndex];

        if (!materialDef.extensions || !materialDef.extensions[this.name]) return null;

        return MeshPhysicalMaterial;

    }

    extendMaterialParams (materialIndex, materialParams) {

        const parser = this.parser;
        const materialDef = parser.json.materials[materialIndex];

        if (!materialDef.extensions || !materialDef.extensions[this.name]) {

            return Promise.resolve();

        }

        const pending = [];

        const extension = materialDef.extensions[this.name];

        if (extension.transmissionFactor !== undefined) {

            materialParams.transmission = extension.transmissionFactor;

        }

        if (extension.transmissionTexture !== undefined) {

            pending.push(parser.assignTexture(materialParams, 'transmissionMap', extension.transmissionTexture));

        }

        return Promise.all(pending);

    }

}

/**
 * Materials Volume Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_volume
 */
class GLTFMaterialsVolumeExtension {

    public name = EXTENSIONS.KHR_MATERIALS_VOLUME;

    public parser: GLTFParser;

    constructor (parser: GLTFParser) {

        this.parser = parser;


    }

    getMaterialType (materialIndex) {

        const parser = this.parser;
        const materialDef = parser.json.materials[materialIndex];

        if (!materialDef.extensions || !materialDef.extensions[this.name]) return null;

        return MeshPhysicalMaterial;

    }

    extendMaterialParams (materialIndex, materialParams) {

        const parser = this.parser;
        const materialDef = parser.json.materials[materialIndex];

        if (!materialDef.extensions || !materialDef.extensions[this.name]) {

            return Promise.resolve();

        }

        const pending = [];

        const extension = materialDef.extensions[this.name];

        materialParams.thickness = extension.thicknessFactor !== undefined ? extension.thicknessFactor : 0;

        if (extension.thicknessTexture !== undefined) {

            pending.push(parser.assignTexture(materialParams, 'thicknessMap', extension.thicknessTexture));

        }

        materialParams.attenuationDistance = extension.attenuationDistance || Infinity;

        const colorArray = extension.attenuationColor || [1, 1, 1];
        materialParams.attenuationColor = new Color(colorArray[0], colorArray[1], colorArray[2]);

        return Promise.all(pending);

    }

}

/**
 * Materials ior Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_ior
 */
class GLTFMaterialsIorExtension {

    public name = EXTENSIONS.KHR_MATERIALS_IOR;

    public parser: GLTFParser;

    constructor (parser: GLTFParser) {

        this.parser = parser;

    }

    getMaterialType (materialIndex) {

        const parser = this.parser;
        const materialDef = parser.json.materials[materialIndex];

        if (!materialDef.extensions || !materialDef.extensions[this.name]) return null;

        return MeshPhysicalMaterial;

    }

    extendMaterialParams (materialIndex, materialParams) {

        const parser = this.parser;
        const materialDef = parser.json.materials[materialIndex];

        if (!materialDef.extensions || !materialDef.extensions[this.name]) {

            return Promise.resolve();

        }

        const extension = materialDef.extensions[this.name];

        materialParams.ior = extension.ior !== undefined ? extension.ior : 1.5;

        return Promise.resolve();

    }

}

/**
 * Materials specular Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_specular
 */
class GLTFMaterialsSpecularExtension {

    public name = EXTENSIONS.KHR_MATERIALS_SPECULAR;

    public parser: GLTFParser;

    constructor (parser: GLTFParser) {

        this.parser = parser;

    }

    getMaterialType (materialIndex) {

        const parser = this.parser;
        const materialDef = parser.json.materials[materialIndex];

        if (!materialDef.extensions || !materialDef.extensions[this.name]) return null;

        return MeshPhysicalMaterial;

    }

    extendMaterialParams (materialIndex, materialParams) {

        const parser = this.parser;
        const materialDef = parser.json.materials[materialIndex];

        if (!materialDef.extensions || !materialDef.extensions[this.name]) {

            return Promise.resolve();

        }

        const pending = [];

        const extension = materialDef.extensions[this.name];

        materialParams.specularIntensity = extension.specularFactor !== undefined ? extension.specularFactor : 1.0;

        if (extension.specularTexture !== undefined) {

            pending.push(parser.assignTexture(materialParams, 'specularIntensityMap', extension.specularTexture));

        }

        const colorArray = extension.specularColorFactor || [1, 1, 1];
        materialParams.specularColor = new Color(colorArray[0], colorArray[1], colorArray[2]);

        if (extension.specularColorTexture !== undefined) {

            pending.push(parser.assignTexture(materialParams, 'specularColorMap', extension.specularColorTexture, sRGBEncoding));

        }

        return Promise.all(pending);

    }

}

/**
 * BasisU Texture Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_texture_basisu
 */
class GLTFTextureBasisUExtension {

    public name = EXTENSIONS.KHR_TEXTURE_BASISU;

    public parser: GLTFParser;

    constructor (parser: GLTFParser) {

        this.parser = parser;
        this.name = EXTENSIONS.KHR_TEXTURE_BASISU;

    }

    loadTexture (textureIndex) {

        const parser = this.parser;
        const json = parser.json;

        const textureDef = json.textures[textureIndex];

        if (!textureDef.extensions || !textureDef.extensions[this.name]) {

            return null;

        }

        const extension = textureDef.extensions[this.name];
        const loader = parser.options.ktx2Loader;

        if (!loader) {

            if (json.extensionsRequired && json.extensionsRequired.indexOf(this.name) >= 0) {

                throw new Error('THREE.GLTFLoader: setKTX2Loader must be called before loading KTX2 textures');

            } else {

                // Assumes that the extension is optional and that a fallback texture is present
                return null;

            }

        }

        return parser.loadTextureImage(textureIndex, extension.source, loader);

    }

}

/**
 * WebP Texture Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_texture_webp
 */
class GLTFTextureWebPExtension {

    public name = EXTENSIONS.EXT_TEXTURE_WEBP;

    public parser: GLTFParser;

    public isSupported?: Promise<boolean>;

    constructor (parser: GLTFParser) {

        this.parser = parser;
        this.isSupported = null;

    }

    loadTexture (textureIndex) {

        const name = this.name;
        const parser = this.parser;
        const json = parser.json;

        const textureDef = json.textures[textureIndex];

        if (!textureDef.extensions || !textureDef.extensions[name]) {

            return null;

        }

        const extension = textureDef.extensions[name];
        const source = json.images[extension.source];

        let loader = parser.textureLoader;
        if (source.uri) {

            const handler = parser.options.manager.getHandler(source.uri);
            if (handler !== null) loader = handler;

        }

        return this.detectSupport().then(function (isSupported) {

            if (isSupported) return parser.loadTextureImage(textureIndex, extension.source, loader);

            if (json.extensionsRequired && json.extensionsRequired.indexOf(name) >= 0) {

                throw new Error('THREE.GLTFLoader: WebP required by asset but unsupported.');

            }

            // Fall back to PNG or JPEG.
            return parser.loadTexture(textureIndex);

        });

    }

    detectSupport () {

        if (!this.isSupported) {

            this.isSupported = new Promise(function (resolve) {

                const image = new Image();

                // Lossy test image. Support for lossy images doesn't guarantee support for all
                // WebP images, unfortunately.
                image.src = '';

                image.onload = image.onerror = function () {

                    resolve(image.height === 1);

                };

            });

        }

        return this.isSupported;

    }

}

/**
 * AVIF Texture Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_texture_avif
 */
class GLTFTextureAVIFExtension {

    public name = EXTENSIONS.EXT_TEXTURE_AVIF;

    public parser: GLTFParser;

    public isSupported?: Promise<boolean>;

    constructor (parser: GLTFParser) {

        this.parser = parser;
        this.isSupported = null;

    }

    loadTexture (textureIndex) {

        const name = this.name;
        const parser = this.parser;
        const json = parser.json;

        const textureDef = json.textures[textureIndex];

        if (!textureDef.extensions || !textureDef.extensions[name]) {

            return null;

        }

        const extension = textureDef.extensions[name];
        const source = json.images[extension.source];

        let loader = parser.textureLoader;
        if (source.uri) {

            const handler = parser.options.manager.getHandler(source.uri);
            if (handler !== null) loader = handler;

        }

        return this.detectSupport().then(function (isSupported) {

            if (isSupported) return parser.loadTextureImage(textureIndex, extension.source, loader);

            if (json.extensionsRequired && json.extensionsRequired.indexOf(name) >= 0) {

                throw new Error('THREE.GLTFLoader: AVIF required by asset but unsupported.');

            }

            // Fall back to PNG or JPEG.
            return parser.loadTexture(textureIndex);

        });

    }

    detectSupport () {

        if (!this.isSupported) {

            this.isSupported = new Promise(function (resolve) {

                const image = new Image();

                // Lossy test image.
                image.src = '';
                image.onload = image.onerror = function () {

                    resolve(image.height === 1);

                };

            });

        }

        return this.isSupported;

    }

}

/**
 * meshopt BufferView Compression Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_meshopt_compression
 */
class GLTFMeshoptCompression {

    public name = EXTENSIONS.EXT_MESHOPT_COMPRESSION;

    public parser: GLTFParser;

    constructor (parser: GLTFParser) {

        this.parser = parser;

    }

    loadBufferView (index) {

        const json = this.parser.json;
        const bufferView = json.bufferViews[index];

        if (bufferView.extensions && bufferView.extensions[this.name]) {

            const extensionDef = bufferView.extensions[this.name];

            const buffer = this.parser.getDependency('buffer', extensionDef.buffer);
            const decoder = this.parser.options.meshoptDecoder;

            if (!decoder || !decoder.supported) {

                if (json.extensionsRequired && json.extensionsRequired.indexOf(this.name) >= 0) {

                    throw new Error('THREE.GLTFLoader: setMeshoptDecoder must be called before loading compressed files');

                } else {

                    // Assumes that the extension is optional and that fallback buffer data is present
                    return null;

                }

            }

            return buffer.then(function (res) {

                const byteOffset = extensionDef.byteOffset || 0;
                const byteLength = extensionDef.byteLength || 0;

                const count = extensionDef.count;
                const stride = extensionDef.byteStride;

                const source = new Uint8Array(res, byteOffset, byteLength);

                if (decoder.decodeGltfBufferAsync) {

                    return decoder.decodeGltfBufferAsync(count, stride, source, extensionDef.mode, extensionDef.filter).then(function (res) {

                        return res.buffer;

                    });

                } else {

                    // Support for MeshoptDecoder 0.18 or earlier, without decodeGltfBufferAsync
                    return decoder.ready.then(function () {

                        const result = new ArrayBuffer(count * stride);
                        decoder.decodeGltfBuffer(new Uint8Array(result), count, stride, source, extensionDef.mode, extensionDef.filter);
                        return result;

                    });

                }

            });

        } else {

            return null;

        }

    }

}

/**
 * GPU Instancing Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_mesh_gpu_instancing
 *
 */
class GLTFMeshGpuInstancing {

    public name = EXTENSIONS.EXT_MESH_GPU_INSTANCING;

    public parser: GLTFParser;

    constructor (parser: GLTFParser) {

        this.parser = parser;

    }

    createNodeMesh (nodeIndex) {

        const json = this.parser.json;
        const nodeDef = json.nodes[nodeIndex];

        if (!nodeDef.extensions || !nodeDef.extensions[this.name] ||
            nodeDef.mesh === undefined) {

            return null;

        }

        const meshDef = json.meshes[nodeDef.mesh];

        // No Points or Lines + Instancing support yet

        for (const primitive of meshDef.primitives) {

            if (primitive.mode !== WEBGL_CONSTANTS.TRIANGLES &&
                primitive.mode !== WEBGL_CONSTANTS.TRIANGLE_STRIP &&
                primitive.mode !== WEBGL_CONSTANTS.TRIANGLE_FAN &&
                primitive.mode !== undefined) {

                return null;

            }

        }

        const extensionDef = nodeDef.extensions[this.name];
        const attributesDef = extensionDef.attributes;

        // @TODO: Can we support InstancedMesh + SkinnedMesh?

        const pending = [];
        const attributes = {};

        for (const key in attributesDef) {

            pending.push(this.parser.getDependency('accessor', attributesDef[key]).then(accessor => {

                attributes[key] = accessor;
                return attributes[key];

            }));

        }

        if (pending.length < 1) {

            return null;

        }

        pending.push(this.parser.createNodeMesh(nodeIndex));

        return Promise.all(pending).then(results => {

            const nodeObject = results.pop();
            const meshes = nodeObject.isGroup ? nodeObject.children : [nodeObject];
            const count = results[0].count; // All attribute counts should be same
            const instancedMeshes = [];

            for (const mesh of meshes) {

                // Temporal variables
                const m = new Matrix4();
                const p = new Vector3();
                const q = new Quaternion();
                const s = new Vector3(1, 1, 1);

                const instancedMesh = new InstancedMesh(mesh.geometry, mesh.material, count);

                for (let i = 0; i < count; i++) {

                    //@ts-ignore
                    if (attributes.TRANSLATION) {
                        //@ts-ignore
                        p.fromBufferAttribute(attributes.TRANSLATION, i);

                    }

                    //@ts-ignore
                    if (attributes.ROTATION) {
                        //@ts-ignore
                        q.fromBufferAttribute(attributes.ROTATION, i);

                    }

                    //@ts-ignore
                    if (attributes.SCALE) {
                        //@ts-ignore
                        s.fromBufferAttribute(attributes.SCALE, i);

                    }

                    instancedMesh.setMatrixAt(i, m.compose(p, q, s));

                }

                // Add instance attributes to the geometry, excluding TRS.
                for (const attributeName in attributes) {

                    if (attributeName !== 'TRANSLATION' &&
                        attributeName !== 'ROTATION' &&
                        attributeName !== 'SCALE') {

                        mesh.geometry.setAttribute(attributeName, attributes[attributeName]);

                    }

                }

                // Just in case
                Object3D.prototype.copy.call(instancedMesh, mesh);

                // https://github.com/mrdoob/three.js/issues/18334
                instancedMesh.frustumCulled = false;
                this.parser.assignFinalMaterial(instancedMesh);

                instancedMeshes.push(instancedMesh);

            }

            if (nodeObject.isGroup) {

                nodeObject.clear();

                nodeObject.add(...instancedMeshes);

                return nodeObject;

            }

            return instancedMeshes[0];

        });

    }

}

/* BINARY EXTENSION */
const BINARY_EXTENSION_HEADER_MAGIC = 'glTF';
const BINARY_EXTENSION_HEADER_LENGTH = 12;
const BINARY_EXTENSION_CHUNK_TYPES = { JSON: 0x4E4F534A, BIN: 0x004E4942 };

class GLTFBinaryExtension {

    public name = EXTENSIONS.KHR_BINARY_GLTF;

    public content = null;
    public body = null;

    public header: Record<string, any>;

    constructor (data: ArrayBufferLike) {

        const headerView = new DataView(data, 0, BINARY_EXTENSION_HEADER_LENGTH);
        const textDecoder = new TextDecoder();

        this.header = {
            magic: textDecoder.decode(new Uint8Array(data.slice(0, 4))),
            version: headerView.getUint32(4, true),
            length: headerView.getUint32(8, true)
        };

        if (this.header.magic !== BINARY_EXTENSION_HEADER_MAGIC) {

            throw new Error('THREE.GLTFLoader: Unsupported glTF-Binary header.');

        } else if (this.header.version < 2.0) {

            throw new Error('THREE.GLTFLoader: Legacy binary file detected.');

        }

        const chunkContentsLength = this.header.length - BINARY_EXTENSION_HEADER_LENGTH;
        const chunkView = new DataView(data, BINARY_EXTENSION_HEADER_LENGTH);
        let chunkIndex = 0;

        while (chunkIndex < chunkContentsLength) {

            const chunkLength = chunkView.getUint32(chunkIndex, true);
            chunkIndex += 4;

            const chunkType = chunkView.getUint32(chunkIndex, true);
            chunkIndex += 4;

            if (chunkType === BINARY_EXTENSION_CHUNK_TYPES.JSON) {

                const contentArray = new Uint8Array(data, BINARY_EXTENSION_HEADER_LENGTH + chunkIndex, chunkLength);
                this.content = textDecoder.decode(contentArray);

            } else if (chunkType === BINARY_EXTENSION_CHUNK_TYPES.BIN) {

                const byteOffset = BINARY_EXTENSION_HEADER_LENGTH + chunkIndex;
                this.body = data.slice(byteOffset, byteOffset + chunkLength);

            }

            // Clients must ignore chunks with unknown types.

            chunkIndex += chunkLength;

        }

        if (this.content === null) {

            throw new Error('THREE.GLTFLoader: JSON content not found.');

        }

    }

}

/**
 * DRACO Mesh Compression Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_draco_mesh_compression
 */
class GLTFDracoMeshCompressionExtension {

    public name = EXTENSIONS.KHR_DRACO_MESH_COMPRESSION;

    public json: any;

    public dracoLoader: DRACOLoader;

    constructor (json: any, dracoLoader: DRACOLoader) {

        if (!dracoLoader) {

            throw new Error('THREE.GLTFLoader: No DRACOLoader instance provided.');

        }
        this.json = json;
        this.dracoLoader = dracoLoader;
        this.dracoLoader.preload();

    }

    decodePrimitive (primitive, parser) {

        const json = this.json;
        const dracoLoader = this.dracoLoader;
        const bufferViewIndex = primitive.extensions[this.name].bufferView;
        const gltfAttributeMap = primitive.extensions[this.name].attributes;
        const threeAttributeMap = {};
        const attributeNormalizedMap = {};
        const attributeTypeMap = {};

        for (const attributeName in gltfAttributeMap) {

            const threeAttributeName = ATTRIBUTES[attributeName] || attributeName.toLowerCase();

            threeAttributeMap[threeAttributeName] = gltfAttributeMap[attributeName];

        }

        for (const attributeName in primitive.attributes) {

            const threeAttributeName = ATTRIBUTES[attributeName] || attributeName.toLowerCase();

            if (gltfAttributeMap[attributeName] !== undefined) {

                const accessorDef = json.accessors[primitive.attributes[attributeName]];
                const componentType = WEBGL_COMPONENT_TYPES[accessorDef.componentType];

                attributeTypeMap[threeAttributeName] = componentType.name;
                attributeNormalizedMap[threeAttributeName] = accessorDef.normalized === true;

            }

        }

        return parser.getDependency('bufferView', bufferViewIndex).then(function (bufferView) {

            return new Promise(function (resolve) {

                dracoLoader.decodeDracoFile(bufferView, function (geometry) {

                    for (const attributeName in geometry.attributes) {

                        const attribute = geometry.attributes[attributeName];
                        const normalized = attributeNormalizedMap[attributeName];

                        if (normalized !== undefined) attribute.normalized = normalized;

                    }

                    resolve(geometry);

                }, threeAttributeMap, attributeTypeMap);

            });

        });

    }

}

/**
 * Texture Transform Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_texture_transform
 */
class GLTFTextureTransformExtension {

    public name = EXTENSIONS.KHR_TEXTURE_TRANSFORM;


    extendTexture (texture, transform) {

        if (transform.texCoord !== undefined) {

            console.warn('THREE.GLTFLoader: Custom UV sets in "' + this.name + '" extension not yet supported.');

        }

        if (transform.offset === undefined && transform.rotation === undefined && transform.scale === undefined) {

            // See https://github.com/mrdoob/three.js/issues/21819.
            return texture;

        }

        texture = texture.clone();

        if (transform.offset !== undefined) {

            texture.offset.fromArray(transform.offset);

        }

        if (transform.rotation !== undefined) {

            texture.rotation = transform.rotation;

        }

        if (transform.scale !== undefined) {

            texture.repeat.fromArray(transform.scale);

        }

        texture.needsUpdate = true;

        return texture;

    }

}

/**
 * Mesh Quantization Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_mesh_quantization
 */
class GLTFMeshQuantizationExtension {


    public name = EXTENSIONS.KHR_MESH_QUANTIZATION;


}

/*********************************/
/********** INTERPOLATION ********/
/*********************************/

// Spline Interpolation
// Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#appendix-c-spline-interpolation
class GLTFCubicSplineInterpolant extends Interpolant {

    constructor (parameterPositions, sampleValues, sampleSize, resultBuffer) {

        super(parameterPositions, sampleValues, sampleSize, resultBuffer);

    }

    copySampleValue_ (index) {

        // Copies a sample value to the result buffer. See description of glTF
        // CUBICSPLINE values layout in interpolate_() function below.

        const result = this.resultBuffer,
            values = this.sampleValues,
            valueSize = this.valueSize,
            offset = index * valueSize * 3 + valueSize;

        for (let i = 0; i !== valueSize; i++) {

            result[i] = values[offset + i];

        }

        return result;

    }

    interpolate_ (i1, t0, t, t1) {

        const result = this.resultBuffer;
        const values = this.sampleValues;
        const stride = this.valueSize;

        const stride2 = stride * 2;
        const stride3 = stride * 3;

        const td = t1 - t0;

        const p = (t - t0) / td;
        const pp = p * p;
        const ppp = pp * p;

        const offset1 = i1 * stride3;
        const offset0 = offset1 - stride3;

        const s2 = - 2 * ppp + 3 * pp;
        const s3 = ppp - pp;
        const s0 = 1 - s2;
        const s1 = s3 - pp + p;

        // Layout of keyframe output values for CUBICSPLINE animations:
        //   [ inTangent_1, splineVertex_1, outTangent_1, inTangent_2, splineVertex_2, ... ]
        for (let i = 0; i !== stride; i++) {

            const p0 = values[offset0 + i + stride]; // splineVertex_k
            const m0 = values[offset0 + i + stride2] * td; // outTangent_k * (t_k+1 - t_k)
            const p1 = values[offset1 + i + stride]; // splineVertex_k+1
            const m1 = values[offset1 + i] * td; // inTangent_k+1 * (t_k+1 - t_k)

            result[i] = s0 * p0 + s1 * m0 + s2 * p1 + s3 * m1;

        }

        return result;

    }

}

const _q = new Quaternion();

class GLTFCubicSplineQuaternionInterpolant extends GLTFCubicSplineInterpolant {

    interpolate_ (i1, t0, t, t1) {

        const result = super.interpolate_(i1, t0, t, t1);

        _q.fromArray(result).normalize().toArray(result);

        return result;

    }

}


/*********************************/
/********** INTERNALS ************/
/*********************************/

/* CONSTANTS */

const WEBGL_CONSTANTS = {
    FLOAT: 5126,
    //FLOAT_MAT2: 35674,
    FLOAT_MAT3: 35675,
    FLOAT_MAT4: 35676,
    FLOAT_VEC2: 35664,
    FLOAT_VEC3: 35665,
    FLOAT_VEC4: 35666,
    LINEAR: 9729,
    REPEAT: 10497,
    SAMPLER_2D: 35678,
    POINTS: 0,
    LINES: 1,
    LINE_LOOP: 2,
    LINE_STRIP: 3,
    TRIANGLES: 4,
    TRIANGLE_STRIP: 5,
    TRIANGLE_FAN: 6,
    UNSIGNED_BYTE: 5121,
    UNSIGNED_SHORT: 5123
};

const WEBGL_COMPONENT_TYPES = {
    5120: Int8Array,
    5121: Uint8Array,
    5122: Int16Array,
    5123: Uint16Array,
    5125: Uint32Array,
    5126: Float32Array
};

const WEBGL_FILTERS = {
    9728: NearestFilter,
    9729: LinearFilter,
    9984: NearestMipmapNearestFilter,
    9985: LinearMipmapNearestFilter,
    9986: NearestMipmapLinearFilter,
    9987: LinearMipmapLinearFilter
};

const WEBGL_WRAPPINGS = {
    33071: ClampToEdgeWrapping,
    33648: MirroredRepeatWrapping,
    10497: RepeatWrapping
};

const WEBGL_TYPE_SIZES = {
    'SCALAR': 1,
    'VEC2': 2,
    'VEC3': 3,
    'VEC4': 4,
    'MAT2': 4,
    'MAT3': 9,
    'MAT4': 16
};

const ATTRIBUTES = {
    POSITION: 'position',
    NORMAL: 'normal',
    TANGENT: 'tangent',
    TEXCOORD_0: 'uv',
    TEXCOORD_1: 'uv2',
    COLOR_0: 'color',
    WEIGHTS_0: 'skinWeight',
    JOINTS_0: 'skinIndex',
};

const PATH_PROPERTIES = {
    scale: 'scale',
    translation: 'position',
    position: 'position',
    rotation: 'quaternion',
    weights: 'morphTargetInfluences'
};

const INTERPOLATION = {
    CUBICSPLINE: undefined, // We use a custom interpolant (GLTFCubicSplineInterpolation) for CUBICSPLINE tracks. Each
    // keyframe track will be initialized with a default interpolation type, then modified.
    LINEAR: InterpolateLinear,
    STEP: InterpolateDiscrete
};

const ALPHA_MODES = {
    OPAQUE: 'OPAQUE',
    MASK: 'MASK',
    BLEND: 'BLEND'
};

/**
 * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#default-material
 */
function createDefaultMaterial (cache) {

    if (cache['DefaultMaterial'] === undefined) {

        cache['DefaultMaterial'] = new MeshStandardMaterial({
            color: 0xFFFFFF,
            emissive: 0x000000,
            metalness: 1,
            roughness: 1,
            transparent: false,
            depthTest: true,
            side: FrontSide
        });

    }

    return cache['DefaultMaterial'];

}

function addUnknownExtensionsToUserData (knownExtensions, object, objectDef) {

    // Add unknown glTF extensions to an object's userData.

    for (const name in objectDef.extensions) {

        if (knownExtensions[name] === undefined) {

            object.userData.gltfExtensions = object.userData.gltfExtensions || {};
            object.userData.gltfExtensions[name] = objectDef.extensions[name];

        }

    }

}

/**
 * @param {Object3D|Material|BufferGeometry} object
 * @param {GLTF.definition} gltfDef
 */
function assignExtrasToUserData (object, gltfDef) {

    if (gltfDef.extras !== undefined) {

        if (typeof gltfDef.extras === 'object') {

            Object.assign(object.userData, gltfDef.extras);

        } else {

            console.warn('THREE.GLTFLoader: Ignoring primitive type .extras, ' + gltfDef.extras);

        }

    }

}

/**
 * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#morph-targets
 *
 * @param {BufferGeometry} geometry
 * @param {Array<GLTF.Target>} targets
 * @param {GLTFParser} parser
 * @return {Promise<BufferGeometry>}
 */
function addMorphTargets (geometry, targets, parser) {

    let hasMorphPosition = false;
    let hasMorphNormal = false;
    let hasMorphColor = false;

    for (let i = 0, il = targets.length; i < il; i++) {

        const target = targets[i];

        if (target.POSITION !== undefined) hasMorphPosition = true;
        if (target.NORMAL !== undefined) hasMorphNormal = true;
        if (target.COLOR_0 !== undefined) hasMorphColor = true;

        if (hasMorphPosition && hasMorphNormal && hasMorphColor) break;

    }

    if (!hasMorphPosition && !hasMorphNormal && !hasMorphColor) return Promise.resolve(geometry);

    const pendingPositionAccessors = [];
    const pendingNormalAccessors = [];
    const pendingColorAccessors = [];

    for (let i = 0, il = targets.length; i < il; i++) {

        const target = targets[i];

        if (hasMorphPosition) {

            const pendingAccessor = target.POSITION !== undefined
                ? parser.getDependency('accessor', target.POSITION)
                : geometry.attributes.position;

            pendingPositionAccessors.push(pendingAccessor);

        }

        if (hasMorphNormal) {

            const pendingAccessor = target.NORMAL !== undefined
                ? parser.getDependency('accessor', target.NORMAL)
                : geometry.attributes.normal;

            pendingNormalAccessors.push(pendingAccessor);

        }

        if (hasMorphColor) {

            const pendingAccessor = target.COLOR_0 !== undefined
                ? parser.getDependency('accessor', target.COLOR_0)
                : geometry.attributes.color;

            pendingColorAccessors.push(pendingAccessor);

        }

    }

    return Promise.all([
        Promise.all(pendingPositionAccessors),
        Promise.all(pendingNormalAccessors),
        Promise.all(pendingColorAccessors)
    ]).then(function (accessors) {

        const morphPositions = accessors[0];
        const morphNormals = accessors[1];
        const morphColors = accessors[2];

        if (hasMorphPosition) geometry.morphAttributes.position = morphPositions;
        if (hasMorphNormal) geometry.morphAttributes.normal = morphNormals;
        if (hasMorphColor) geometry.morphAttributes.color = morphColors;
        geometry.morphTargetsRelative = true;

        return geometry;

    });

}

/**
 * @param {Mesh} mesh
 * @param {GLTF.Mesh} meshDef
 */
function updateMorphTargets (mesh, meshDef) {

    mesh.updateMorphTargets();

    if (meshDef.weights !== undefined) {

        for (let i = 0, il = meshDef.weights.length; i < il; i++) {

            mesh.morphTargetInfluences[i] = meshDef.weights[i];

        }

    }

    // .extras has user-defined data, so check that .extras.targetNames is an array.
    if (meshDef.extras && Array.isArray(meshDef.extras.targetNames)) {

        const targetNames = meshDef.extras.targetNames;

        if (mesh.morphTargetInfluences.length === targetNames.length) {

            mesh.morphTargetDictionary = {};

            for (let i = 0, il = targetNames.length; i < il; i++) {

                mesh.morphTargetDictionary[targetNames[i]] = i;

            }

        } else {

            console.warn('THREE.GLTFLoader: Invalid extras.targetNames length. Ignoring names.');

        }

    }

}

function createPrimitiveKey (primitiveDef) {

    const dracoExtension = primitiveDef.extensions && primitiveDef.extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION];
    let geometryKey;

    if (dracoExtension) {

        geometryKey = 'draco:' + dracoExtension.bufferView
            + ':' + dracoExtension.indices
            + ':' + createAttributesKey(dracoExtension.attributes);

    } else {

        geometryKey = primitiveDef.indices + ':' + createAttributesKey(primitiveDef.attributes) + ':' + primitiveDef.mode;

    }

    return geometryKey;

}

function createAttributesKey (attributes) {

    let attributesKey = '';

    const keys = Object.keys(attributes).sort();

    for (let i = 0, il = keys.length; i < il; i++) {

        attributesKey += keys[i] + ':' + attributes[keys[i]] + ';';

    }

    return attributesKey;

}

function getNormalizedComponentScale (constructor) {

    // Reference:
    // https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_mesh_quantization#encoding-quantized-data

    switch (constructor) {

        case Int8Array:
            return 1 / 127;

        case Uint8Array:
            return 1 / 255;

        case Int16Array:
            return 1 / 32767;

        case Uint16Array:
            return 1 / 65535;

        default:
            throw new Error('THREE.GLTFLoader: Unsupported normalized accessor component type.');

    }

}

function getImageURIMimeType (uri) {

    if (uri.search(/\.jpe?g($|\?)/i) > 0 || uri.search(/^data\:image\/jpeg/) === 0) return 'image/jpeg';
    if (uri.search(/\.webp($|\?)/i) > 0 || uri.search(/^data\:image\/webp/) === 0) return 'image/webp';

    return 'image/png';

}

const _identityMatrix = new Matrix4();

/* GLTF PARSER */

class GLTFParser {

    public json: any;

    public extensions: Record<string, any>;

    public plugins: Record<string, PluginCallback>;

    public options: Record<string, any>;

    public cache: GLTFRegistry;

    public associations: Map<Object, any>;

    public primitiveCache: Record<string, any>;

    public nodeCache: Record<string, any>;

    public meshCache = { refs: {}, uses: {} };
    public cameraCache = { refs: {}, uses: {} };
    public lightCache = { refs: {}, uses: {} };

    public sourceCache = {};
    public textureCache = {};

    public nodeNamesUsed = {};

    public fileLoader: FileLoader;

    public textureLoader: TextureLoader | ImageBitmapLoader;

    constructor (json = {}, options = {}) {

        this.json = json;
        this.extensions = {};
        this.plugins = {};
        this.options = options;

        // loader object cache
        this.cache = new GLTFRegistry();

        // associations between Three.js objects and glTF elements
        this.associations = new Map();

        // BufferGeometry caching
        this.primitiveCache = {};

        // Node cache
        this.nodeCache = {};

        // Object3D instance caches
        this.meshCache = { refs: {}, uses: {} };
        this.cameraCache = { refs: {}, uses: {} };
        this.lightCache = { refs: {}, uses: {} };

        this.sourceCache = {};
        this.textureCache = {};

        // Track node names, to ensure no duplicates
        this.nodeNamesUsed = {};

        // Use an ImageBitmapLoader if imageBitmaps are supported. Moves much of the
        // expensive work of uploading a texture to the GPU off the main thread.

        let isSafari = false;
        let isFirefox = false;
        let firefoxVersion = - 1;

        if (typeof navigator !== 'undefined') {

            isSafari = /^((?!chrome|android).)*safari/i.test(navigator.userAgent) === true;
            isFirefox = navigator.userAgent.indexOf('Firefox') > - 1;
            firefoxVersion = isFirefox ? Number(navigator.userAgent.match(/Firefox\/([0-9]+)\./)[1]) : - 1;

        }

        if (typeof createImageBitmap === 'undefined' || isSafari || (isFirefox && firefoxVersion < 98)) {

            this.textureLoader = new TextureLoader(this.options.manager);

        } else {

            this.textureLoader = new ImageBitmapLoader(this.options.manager);
            this.textureLoader.setLoadInWorker(true);
        }

        this.textureLoader.setCrossOrigin(this.options.crossOrigin);
        this.textureLoader.setRequestHeader(this.options.requestHeader);

        this.fileLoader = new FileLoader(this.options.manager);
        this.fileLoader.setResponseType(XHRResponseType.ARRAYBUFFER);
        this.fileLoader.setLoadInWorker(true);

        if (this.options.crossOrigin === 'use-credentials') {

            this.fileLoader.setWithCredentials(true);

        }

    }

    public setExtensions (extensions: Record<string, any>) {

        this.extensions = extensions;

    }

    public setPlugins (plugins: Record<string, PluginCallback>) {

        this.plugins = plugins;

    }

    public parse (onLoad?: OnLoad, onError?: OnError) {

        const parser = this;
        const json = this.json;
        const extensions = this.extensions;

        // Clear the loader cache
        this.cache.removeAll();
        this.nodeCache = {};

        // Mark the special nodes/meshes in json for efficient parse
        this._invokeAll(function (ext) {

            return ext._markDefs && ext._markDefs();

        });

        Promise.all(this._invokeAll(function (ext) {

            return ext.beforeRoot && ext.beforeRoot();

        })).then(function () {

            return Promise.all([

                parser.getDependencies('scene'),
                parser.getDependencies('animation'),
                parser.getDependencies('camera'),

            ]);

        }).then(function (dependencies) {

            const result = {
                scene: dependencies[0][json.scene || 0],
                scenes: dependencies[0],
                animations: dependencies[1],
                cameras: dependencies[2],
                asset: json.asset,
                parser: parser,
                userData: {}
            };

            addUnknownExtensionsToUserData(extensions, result, json);

            assignExtrasToUserData(result, json);

            Promise.all(parser._invokeAll(function (ext) {

                return ext.afterRoot && ext.afterRoot(result);

            })).then(function () {

                if (onLoad) onLoad(result);

            });

        }).catch(onError);

    }

    /**
     * Marks the special nodes/meshes in json for efficient parse.
     */
    private _markDefs () {

        const nodeDefs = this.json.nodes || [];
        const skinDefs = this.json.skins || [];
        const meshDefs = this.json.meshes || [];

        // Nothing in the node definition indicates whether it is a Bone or an
        // Object3D. Use the skins' joint references to mark bones.
        for (let skinIndex = 0, skinLength = skinDefs.length; skinIndex < skinLength; skinIndex++) {

            const joints = skinDefs[skinIndex].joints;

            for (let i = 0, il = joints.length; i < il; i++) {

                nodeDefs[joints[i]].isBone = true;

            }

        }

        // Iterate over all nodes, marking references to shared resources,
        // as well as skeleton joints.
        for (let nodeIndex = 0, nodeLength = nodeDefs.length; nodeIndex < nodeLength; nodeIndex++) {

            const nodeDef = nodeDefs[nodeIndex];

            if (nodeDef.mesh !== undefined) {

                this._addNodeRef(this.meshCache, nodeDef.mesh);

                // Nothing in the mesh definition indicates whether it is
                // a SkinnedMesh or Mesh. Use the node's mesh reference
                // to mark SkinnedMesh if node has skin.
                if (nodeDef.skin !== undefined) {

                    meshDefs[nodeDef.mesh].isSkinnedMesh = true;

                }

            }

            if (nodeDef.camera !== undefined) {

                this._addNodeRef(this.cameraCache, nodeDef.camera);

            }

        }

    }

    /**
     * Counts references to shared node / Object3D resources. These resources
     * can be reused, or "instantiated", at multiple nodes in the scene
     * hierarchy. Mesh, Camera, and Light instances are instantiated and must
     * be marked. Non-scenegraph resources (like Materials, Geometries, and
     * Textures) can be reused directly and are not marked here.
     *
     * Example: CesiumMilkTruck sample model reuses "Wheel" meshes.
     */
    private _addNodeRef (cache, index) {

        if (index === undefined) return;

        if (cache.refs[index] === undefined) {

            cache.refs[index] = cache.uses[index] = 0;

        }

        cache.refs[index]++;

    }

    /** Returns a reference to a shared resource, cloning it if necessary. */
    private _getNodeRef (cache, index, object) {

        if (cache.refs[index] <= 1) return object;

        const ref = object.clone();

        // Propagates mappings to the cloned object, prevents mappings on the
        // original object from being lost.
        const updateMappings = (original, clone) => {

            const mappings = this.associations.get(original);
            if (mappings != null) {

                this.associations.set(clone, mappings);

            }

            for (const [i, child] of original.children.entries()) {

                updateMappings(child, clone.children[i]);

            }

        };

        updateMappings(object, ref);

        ref.name += '_instance_' + (cache.uses[index]++);

        return ref;

    }

    private _invokeOne (func) {

        const extensions = Object.values(this.plugins);
        //@ts-ignore
        extensions.push(this);

        for (let i = 0; i < extensions.length; i++) {

            const result = func(extensions[i]);

            if (result) return result;

        }

        return null;

    }

    _invokeAll (func) {

        const extensions = Object.values(this.plugins);
        //@ts-ignore
        extensions.unshift(this);

        const pending = [];

        for (let i = 0; i < extensions.length; i++) {

            const result = func(extensions[i]);

            if (result) pending.push(result);

        }

        return pending;

    }

    /**
     * Requests the specified dependency asynchronously, with caching.
     * @param {string} type
     * @param {number} index
     * @return {Promise<Object3D|Material|THREE.Texture|AnimationClip|ArrayBuffer|Object>}
     */
    public getDependency (type: string, index: number) {

        const cacheKey = type + ':' + index;
        let dependency = this.cache.get(cacheKey);

        if (!dependency) {

            switch (type) {

                case 'scene':
                    dependency = this.loadScene(index);
                    break;

                case 'node':
                    dependency = this._invokeOne(function (ext) {

                        return ext.loadNode && ext.loadNode(index);

                    });
                    break;

                case 'mesh':
                    dependency = this._invokeOne(function (ext) {

                        return ext.loadMesh && ext.loadMesh(index);

                    });
                    break;

                case 'accessor':
                    dependency = this.loadAccessor(index);
                    break;

                case 'bufferView':
                    dependency = this._invokeOne(function (ext) {

                        return ext.loadBufferView && ext.loadBufferView(index);

                    });
                    break;

                case 'buffer':
                    dependency = this.loadBuffer(index);
                    break;

                case 'material':
                    dependency = this._invokeOne(function (ext) {

                        return ext.loadMaterial && ext.loadMaterial(index);

                    });
                    break;

                case 'texture':
                    dependency = this._invokeOne(function (ext) {

                        return ext.loadTexture && ext.loadTexture(index);

                    });
                    break;

                case 'skin':
                    dependency = this.loadSkin(index);
                    break;

                case 'animation':
                    dependency = this._invokeOne(function (ext) {

                        return ext.loadAnimation && ext.loadAnimation(index);

                    });
                    break;

                case 'camera':
                    dependency = this.loadCamera(index);
                    break;

                default:
                    dependency = this._invokeOne(function (ext) {

                        return ext != this && ext.getDependency && ext.getDependency(type, index);

                    });

                    if (!dependency) {

                        throw new Error('Unknown type: ' + type);

                    }

                    break;

            }

            this.cache.add(cacheKey, dependency);

        }

        return dependency;

    }

    /**
     * Requests all dependencies of the specified type asynchronously, with caching.
     * @param {string} type
     * @return {Promise<Array<Object>>}
     */
    getDependencies (type) {

        let dependencies = this.cache.get(type);

        if (!dependencies) {

            const parser = this;
            const defs = this.json[type + (type === 'mesh' ? 'es' : 's')] || [];

            dependencies = Promise.all(defs.map(function (def, index) {

                return parser.getDependency(type, index);

            }));

            this.cache.add(type, dependencies);

        }

        return dependencies;

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
     * @param {number} bufferIndex
     * @return {Promise<ArrayBuffer>}
     */
    public loadBuffer (bufferIndex: number): Promise<ArrayBuffer> {

        const bufferDef = this.json.buffers[bufferIndex];
        const loader = this.fileLoader;

        if (bufferDef.type && bufferDef.type !== 'arraybuffer') {

            throw new Error('THREE.GLTFLoader: ' + bufferDef.type + ' buffer type is not supported.');

        }

        // If present, GLB container is required to be the first buffer.
        if (bufferDef.uri === undefined && bufferIndex === 0) {

            return Promise.resolve(this.extensions[EXTENSIONS.KHR_BINARY_GLTF].body);

        }

        const options = this.options;

        return new Promise(function (resolve, reject) {

            loader.load(LoaderUtils.resolveURL(bufferDef.uri, options.path), resolve, undefined, function () {

                reject(new Error('THREE.GLTFLoader: Failed to load buffer "' + bufferDef.uri + '".'));

            });

        });

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
     * @param {number} bufferViewIndex
     * @return {Promise<ArrayBuffer>}
     */
    public loadBufferView (bufferViewIndex: number): Promise<ArrayBuffer> {

        const bufferViewDef = this.json.bufferViews[bufferViewIndex];

        return this.getDependency('buffer', bufferViewDef.buffer).then(function (buffer) {

            const byteLength = bufferViewDef.byteLength || 0;
            const byteOffset = bufferViewDef.byteOffset || 0;
            return buffer.slice(byteOffset, byteOffset + byteLength);

        });

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#accessors
     * @param {number} accessorIndex
     * @return {Promise<BufferAttribute|InterleavedBufferAttribute>}
     */
    public loadAccessor (accessorIndex: number): Promise<BufferAttribute | InterleavedBufferAttribute> {

        const parser = this;
        const json = this.json;

        const accessorDef = this.json.accessors[accessorIndex];

        if (accessorDef.bufferView === undefined && accessorDef.sparse === undefined) {

            const itemSize = WEBGL_TYPE_SIZES[accessorDef.type];
            const TypedArray = WEBGL_COMPONENT_TYPES[accessorDef.componentType];
            const normalized = accessorDef.normalized === true;

            const array = new TypedArray(accessorDef.count * itemSize);
            return Promise.resolve(new BufferAttribute(array, itemSize, normalized));

        }

        const pendingBufferViews = [];

        if (accessorDef.bufferView !== undefined) {

            pendingBufferViews.push(this.getDependency('bufferView', accessorDef.bufferView));

        } else {

            pendingBufferViews.push(null);

        }

        if (accessorDef.sparse !== undefined) {

            pendingBufferViews.push(this.getDependency('bufferView', accessorDef.sparse.indices.bufferView));
            pendingBufferViews.push(this.getDependency('bufferView', accessorDef.sparse.values.bufferView));

        }

        return Promise.all(pendingBufferViews).then(function (bufferViews) {

            const bufferView = bufferViews[0];

            const itemSize = WEBGL_TYPE_SIZES[accessorDef.type];
            const TypedArray = WEBGL_COMPONENT_TYPES[accessorDef.componentType];

            // For VEC3: itemSize is 3, elementBytes is 4, itemBytes is 12.
            const elementBytes = TypedArray.BYTES_PER_ELEMENT;
            const itemBytes = elementBytes * itemSize;
            const byteOffset = accessorDef.byteOffset || 0;
            const byteStride = accessorDef.bufferView !== undefined ? json.bufferViews[accessorDef.bufferView].byteStride : undefined;
            const normalized = accessorDef.normalized === true;
            let array, bufferAttribute;

            // The buffer is not interleaved if the stride is the item size in bytes.
            if (byteStride && byteStride !== itemBytes) {

                // Each "slice" of the buffer, as defined by 'count' elements of 'byteStride' bytes, gets its own InterleavedBuffer
                // This makes sure that IBA.count reflects accessor.count properly
                const ibSlice = Math.floor(byteOffset / byteStride);
                const ibCacheKey = 'InterleavedBuffer:' + accessorDef.bufferView + ':' + accessorDef.componentType + ':' + ibSlice + ':' + accessorDef.count;
                let ib = parser.cache.get(ibCacheKey);

                if (!ib) {

                    array = new TypedArray(bufferView, ibSlice * byteStride, accessorDef.count * byteStride / elementBytes);

                    // Integer parameters to IB/IBA are in array elements, not bytes.
                    ib = new InterleavedBuffer(array, byteStride / elementBytes);

                    parser.cache.add(ibCacheKey, ib);

                }

                bufferAttribute = new InterleavedBufferAttribute(ib, itemSize, (byteOffset % byteStride) / elementBytes, normalized);

            } else {

                if (bufferView === null) {

                    array = new TypedArray(accessorDef.count * itemSize);

                } else {

                    array = new TypedArray(bufferView, byteOffset, accessorDef.count * itemSize);

                }

                bufferAttribute = new BufferAttribute(array, itemSize, normalized);

            }

            // https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#sparse-accessors
            if (accessorDef.sparse !== undefined) {

                const itemSizeIndices = WEBGL_TYPE_SIZES.SCALAR;
                const TypedArrayIndices = WEBGL_COMPONENT_TYPES[accessorDef.sparse.indices.componentType];

                const byteOffsetIndices = accessorDef.sparse.indices.byteOffset || 0;
                const byteOffsetValues = accessorDef.sparse.values.byteOffset || 0;

                const sparseIndices = new TypedArrayIndices(bufferViews[1], byteOffsetIndices, accessorDef.sparse.count * itemSizeIndices);
                const sparseValues = new TypedArray(bufferViews[2], byteOffsetValues, accessorDef.sparse.count * itemSize);

                if (bufferView !== null) {

                    // Avoid modifying the original ArrayBuffer, if the bufferView wasn't initialized with zeroes.
                    bufferAttribute = new BufferAttribute(bufferAttribute.array.slice(), bufferAttribute.itemSize, bufferAttribute.normalized);

                }

                for (let i = 0, il = sparseIndices.length; i < il; i++) {

                    const index = sparseIndices[i];

                    bufferAttribute.setX(index, sparseValues[i * itemSize]);
                    if (itemSize >= 2) bufferAttribute.setY(index, sparseValues[i * itemSize + 1]);
                    if (itemSize >= 3) bufferAttribute.setZ(index, sparseValues[i * itemSize + 2]);
                    if (itemSize >= 4) bufferAttribute.setW(index, sparseValues[i * itemSize + 3]);
                    if (itemSize >= 5) throw new Error('THREE.GLTFLoader: Unsupported itemSize in sparse BufferAttribute.');

                }

            }

            return bufferAttribute;

        });

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#textures
     * @param {number} textureIndex
     * @return {Promise<THREE.Texture|null>}
     */
    public loadTexture (textureIndex: number): Promise<Texture | null> {

        const json = this.json;
        const options = this.options;
        const textureDef = json.textures[textureIndex];
        const sourceIndex = textureDef.source;
        const sourceDef = json.images[sourceIndex];

        let loader = this.textureLoader;

        if (sourceDef.uri) {

            const handler = options.manager.getHandler(sourceDef.uri);
            if (handler !== null) loader = handler;

        }

        return this.loadTextureImage(textureIndex, sourceIndex, loader);

    }

    public loadTextureImage (textureIndex: number, sourceIndex: number, loader: TextureLoader | ImageBitmapLoader): Promise<Texture | null> {

        const parser = this;
        const json = this.json;

        const textureDef = json.textures[textureIndex];
        const sourceDef = json.images[sourceIndex];

        const cacheKey = (sourceDef.uri || sourceDef.bufferView) + ':' + textureDef.sampler;

        if (this.textureCache[cacheKey]) {

            // See https://github.com/mrdoob/three.js/issues/21559.
            return this.textureCache[cacheKey];

        }

        const promise = this.loadImageSource(sourceIndex, loader).then(function (texture) {

            texture.flipY = false;

            texture.name = textureDef.name || sourceDef.name || '';

            const samplers = json.samplers || {};
            const sampler = samplers[textureDef.sampler] || {};

            texture.magFilter = WEBGL_FILTERS[sampler.magFilter] || LinearFilter;
            texture.minFilter = WEBGL_FILTERS[sampler.minFilter] || LinearMipmapLinearFilter;
            texture.wrapS = WEBGL_WRAPPINGS[sampler.wrapS] || RepeatWrapping;
            texture.wrapT = WEBGL_WRAPPINGS[sampler.wrapT] || RepeatWrapping;

            parser.associations.set(texture, { textures: textureIndex });

            return texture;

        }).catch(function () {

            return null;

        });

        this.textureCache[cacheKey] = promise;

        return promise;

    }

    public loadImageSource (sourceIndex: number, loader: TextureLoader | ImageBitmapLoader): Promise<Texture | null> {

        const parser = this;
        const json = this.json;
        const options = this.options;

        if (this.sourceCache[sourceIndex] !== undefined) {

            return this.sourceCache[sourceIndex].then((texture) => texture.clone());

        }

        const sourceDef = json.images[sourceIndex];

        const URL = self.URL || self.webkitURL;

        let sourceURI = sourceDef.uri || '';
        let isObjectURL = false;

        if (sourceDef.bufferView !== undefined) {

            // Load binary image data from bufferView, if provided.

            sourceURI = parser.getDependency('bufferView', sourceDef.bufferView).then(function (bufferView) {

                isObjectURL = true;
                const blob = new Blob([bufferView], { type: sourceDef.mimeType });
                sourceURI = URL.createObjectURL(blob);
                return sourceURI;

            });

        } else if (sourceDef.uri === undefined) {

            throw new Error('THREE.GLTFLoader: Image ' + sourceIndex + ' is missing URI and bufferView');

        }

        const promise = Promise.resolve(sourceURI).then(function (sourceURI) {

            return new Promise(function (resolve, reject) {

                let onLoad = resolve;

                if (loader instanceof ImageBitmapLoader) {

                    onLoad = function (imageBitmap: ImageBitmap) {

                        const texture = new Texture(imageBitmap);
                        texture.needsUpdate = true;

                        resolve(texture);

                    };

                }

                loader.load(LoaderUtils.resolveURL(sourceURI, options.path), onLoad, undefined, reject);

            });

        }).then(function (texture: Texture) {

            // Clean up resources and configure Texture.

            if (isObjectURL === true) {

                URL.revokeObjectURL(sourceURI);

            }

            texture.userData.mimeType = sourceDef.mimeType || getImageURIMimeType(sourceDef.uri);

            return texture;

        }).catch(function (error) {

            console.error('THREE.GLTFLoader: Couldn\'t load texture', sourceURI);
            throw error;

        });

        this.sourceCache[sourceIndex] = promise;
        return promise;

    }

    /**
     * Asynchronously assigns a texture to the given material parameters.
     * @param {Object} materialParams
     * @param {string} mapName
     * @param {Object} mapDef
     * @return {Promise<Texture>}
     */
    public assignTexture (materialParams: any, mapName: string, mapDef: any, encoding?: any): Promise<Texture> {

        const parser = this;

        return this.getDependency('texture', mapDef.index).then(function (texture: Texture) {

            if (!texture) return null;

            // Materials sample aoMap from UV set 1 and other maps from UV set 0 - this can't be configured
            // However, we will copy UV set 0 to UV set 1 on demand for aoMap
            if (mapDef.texCoord !== undefined && mapDef.texCoord != 0 && !(mapName === 'aoMap' && mapDef.texCoord == 1)) {

                console.warn('THREE.GLTFLoader: Custom UV set ' + mapDef.texCoord + ' for texture ' + mapName + ' not yet supported.');

            }

            if (parser.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM]) {

                const transform = mapDef.extensions !== undefined ? mapDef.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM] : undefined;

                if (transform) {

                    const gltfReference = parser.associations.get(texture);
                    texture = parser.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM].extendTexture(texture, transform);
                    parser.associations.set(texture, gltfReference);

                }

            }

            if (encoding !== undefined) {

                texture.encoding = encoding;

            }

            materialParams[mapName] = texture;

            return texture;

        });

    }

    /**
     * Assigns final material to a Mesh, Line, or Points instance. The instance
     * already has a material (generated from the glTF material options alone)
     * but reuse of the same glTF material may require multiple threejs materials
     * to accommodate different primitive types, defines, etc. New materials will
     * be created if necessary, and reused from a cache.
     * @param  {Object3D} mesh Mesh, Line, or Points instance.
     */
    public assignFinalMaterial (mesh: any) {

        const geometry = mesh.geometry;
        let material = mesh.material;

        const useDerivativeTangents = geometry.attributes.tangent === undefined;
        const useVertexColors = geometry.attributes.color !== undefined;
        const useFlatShading = geometry.attributes.normal === undefined;

        if (mesh.isPoints) {

            const cacheKey = 'PointsMaterial:' + material.uuid;

            let pointsMaterial = this.cache.get(cacheKey);

            if (!pointsMaterial) {

                pointsMaterial = new PointsMaterial();
                Material.prototype.copy.call(pointsMaterial, material);
                pointsMaterial.color.copy(material.color);
                pointsMaterial.map = material.map;
                pointsMaterial.sizeAttenuation = false; // glTF spec says points should be 1px

                this.cache.add(cacheKey, pointsMaterial);

            }

            material = pointsMaterial;

        } else if (mesh.isLine) {

            const cacheKey = 'LineBasicMaterial:' + material.uuid;

            let lineMaterial = this.cache.get(cacheKey);

            if (!lineMaterial) {

                lineMaterial = new LineBasicMaterial();
                Material.prototype.copy.call(lineMaterial, material);
                lineMaterial.color.copy(material.color);

                this.cache.add(cacheKey, lineMaterial);

            }

            material = lineMaterial;

        }

        // Clone the material if it will be modified
        if (useDerivativeTangents || useVertexColors || useFlatShading) {

            let cacheKey = 'ClonedMaterial:' + material.uuid + ':';

            if (useDerivativeTangents) cacheKey += 'derivative-tangents:';
            if (useVertexColors) cacheKey += 'vertex-colors:';
            if (useFlatShading) cacheKey += 'flat-shading:';

            let cachedMaterial = this.cache.get(cacheKey);

            if (!cachedMaterial) {

                cachedMaterial = material.clone();

                if (useVertexColors) cachedMaterial.vertexColors = true;
                if (useFlatShading) cachedMaterial.flatShading = true;

                if (useDerivativeTangents) {

                    // https://github.com/mrdoob/three.js/issues/11438#issuecomment-507003995
                    if (cachedMaterial.normalScale) cachedMaterial.normalScale.y *= - 1;
                    if (cachedMaterial.clearcoatNormalScale) cachedMaterial.clearcoatNormalScale.y *= - 1;

                }

                this.cache.add(cacheKey, cachedMaterial);

                this.associations.set(cachedMaterial, this.associations.get(material));

            }

            material = cachedMaterial;

        }

        // workarounds for mesh and geometry

        if (material.aoMap && geometry.attributes.uv2 === undefined && geometry.attributes.uv !== undefined) {

            geometry.setAttribute('uv2', geometry.attributes.uv);

        }

        mesh.material = material;

    }

    public getMaterialType ( /* materialIndex */) {

        return MeshStandardMaterial;

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#materials
     * @param {number} materialIndex
     * @return {Promise<Material>}
     */
    public loadMaterial (materialIndex: number): Promise<Material> {

        const parser = this;
        const json = this.json;
        const extensions = this.extensions;
        const materialDef = json.materials[materialIndex];

        let materialType;
        const materialParams: Record<string, any> = {};
        const materialExtensions = materialDef.extensions || {};

        const pending = [];

        if (materialExtensions[EXTENSIONS.KHR_MATERIALS_UNLIT]) {

            const kmuExtension = extensions[EXTENSIONS.KHR_MATERIALS_UNLIT];
            materialType = kmuExtension.getMaterialType();
            pending.push(kmuExtension.extendParams(materialParams, materialDef, parser));

        } else {

            // Specification:
            // https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#metallic-roughness-material

            const metallicRoughness = materialDef.pbrMetallicRoughness || {};

            materialParams.color = new Color(1.0, 1.0, 1.0);
            materialParams.opacity = 1.0;

            if (Array.isArray(metallicRoughness.baseColorFactor)) {

                const array = metallicRoughness.baseColorFactor;

                materialParams.color.fromArray(array);
                materialParams.opacity = array[3];

            }

            if (metallicRoughness.baseColorTexture !== undefined) {

                pending.push(parser.assignTexture(materialParams, 'map', metallicRoughness.baseColorTexture, sRGBEncoding));

            }

            materialParams.metalness = metallicRoughness.metallicFactor !== undefined ? metallicRoughness.metallicFactor : 1.0;
            materialParams.roughness = metallicRoughness.roughnessFactor !== undefined ? metallicRoughness.roughnessFactor : 1.0;

            if (metallicRoughness.metallicRoughnessTexture !== undefined) {

                pending.push(parser.assignTexture(materialParams, 'metalnessMap', metallicRoughness.metallicRoughnessTexture));
                pending.push(parser.assignTexture(materialParams, 'roughnessMap', metallicRoughness.metallicRoughnessTexture));

            }

            materialType = this._invokeOne(function (ext) {

                return ext.getMaterialType && ext.getMaterialType(materialIndex);

            });

            pending.push(Promise.all(this._invokeAll(function (ext) {

                return ext.extendMaterialParams && ext.extendMaterialParams(materialIndex, materialParams);

            })));

        }

        if (materialDef.doubleSided === true) {

            materialParams.side = DoubleSide;

        }

        const alphaMode = materialDef.alphaMode || ALPHA_MODES.OPAQUE;

        if (alphaMode === ALPHA_MODES.BLEND) {

            materialParams.transparent = true;

            // See: https://github.com/mrdoob/three.js/issues/17706
            materialParams.depthWrite = false;

        } else {

            materialParams.transparent = false;

            if (alphaMode === ALPHA_MODES.MASK) {

                materialParams.alphaTest = materialDef.alphaCutoff !== undefined ? materialDef.alphaCutoff : 0.5;

            }

        }

        if (materialDef.normalTexture !== undefined && materialType !== MeshBasicMaterial) {

            pending.push(parser.assignTexture(materialParams, 'normalMap', materialDef.normalTexture));

            materialParams.normalScale = new Vector2(1, 1);

            if (materialDef.normalTexture.scale !== undefined) {

                const scale = materialDef.normalTexture.scale;

                materialParams.normalScale.set(scale, scale);

            }

        }

        if (materialDef.occlusionTexture !== undefined && materialType !== MeshBasicMaterial) {

            pending.push(parser.assignTexture(materialParams, 'aoMap', materialDef.occlusionTexture));

            if (materialDef.occlusionTexture.strength !== undefined) {

                materialParams.aoMapIntensity = materialDef.occlusionTexture.strength;

            }

        }

        if (materialDef.emissiveFactor !== undefined && materialType !== MeshBasicMaterial) {

            materialParams.emissive = new Color().fromArray(materialDef.emissiveFactor);

        }

        if (materialDef.emissiveTexture !== undefined && materialType !== MeshBasicMaterial) {

            pending.push(parser.assignTexture(materialParams, 'emissiveMap', materialDef.emissiveTexture, sRGBEncoding));

        }

        return Promise.all(pending).then(function () {

            const material = new materialType(materialParams);

            if (materialDef.name) material.name = materialDef.name;

            assignExtrasToUserData(material, materialDef);

            parser.associations.set(material, { materials: materialIndex });

            if (materialDef.extensions) addUnknownExtensionsToUserData(extensions, material, materialDef);

            return material;

        });

    }

    /** When Object3D instances are targeted by animation, they need unique names. */
    public createUniqueName (originalName: string) {

        const sanitizedName = PropertyBinding.sanitizeNodeName(originalName || '');

        let name = sanitizedName;

        for (let i = 1; this.nodeNamesUsed[name]; ++i) {

            name = sanitizedName + '_' + i;

        }

        this.nodeNamesUsed[name] = true;

        return name;

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#geometry
     *
     * Creates BufferGeometries from primitives.
     *
     * @param {Array<GLTF.Primitive>} primitives
     * @return {Promise<Array<BufferGeometry>>}
     */
    public loadGeometries (primitives: any): Promise<BufferGeometry[]> {

        const parser = this;
        const extensions = this.extensions;
        const cache = this.primitiveCache;

        function createDracoPrimitive (primitive) {

            return extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION]
                .decodePrimitive(primitive, parser)
                .then(function (geometry) {

                    return addPrimitiveAttributes(geometry, primitive, parser);

                });

        }

        const pending = [];

        for (let i = 0, il = primitives.length; i < il; i++) {

            const primitive = primitives[i];
            const cacheKey = createPrimitiveKey(primitive);

            // See if we've already created this geometry
            const cached = cache[cacheKey];

            if (cached) {

                // Use the cached geometry if it exists
                pending.push(cached.promise);

            } else {

                let geometryPromise;

                if (primitive.extensions && primitive.extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION]) {

                    // Use DRACO geometry if available
                    geometryPromise = createDracoPrimitive(primitive);

                } else {

                    // Otherwise create a new geometry
                    geometryPromise = addPrimitiveAttributes(new BufferGeometry(), primitive, parser);

                }

                // Cache this geometry
                cache[cacheKey] = { primitive: primitive, promise: geometryPromise };

                pending.push(geometryPromise);

            }

        }

        return Promise.all(pending);

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#meshes
     * @param {number} meshIndex
     * @return {Promise<Group|Mesh|SkinnedMesh>}
     */
    public loadMesh (meshIndex: number): Promise<Group | Mesh | SkinnedMesh> {

        const parser = this;
        const json = this.json;
        const extensions = this.extensions;

        const meshDef = json.meshes[meshIndex];
        const primitives = meshDef.primitives;

        const pending = [];

        for (let i = 0, il = primitives.length; i < il; i++) {

            const material = primitives[i].material === undefined
                ? createDefaultMaterial(this.cache)
                : this.getDependency('material', primitives[i].material);

            pending.push(material);

        }

        pending.push(parser.loadGeometries(primitives));

        return Promise.all(pending).then(function (results) {

            const materials = results.slice(0, results.length - 1);
            const geometries = results[results.length - 1];

            const meshes = [];

            for (let i = 0, il = geometries.length; i < il; i++) {

                const geometry = geometries[i];
                const primitive = primitives[i];

                // 1. create Mesh

                let mesh;

                const material = materials[i];

                if (primitive.mode === WEBGL_CONSTANTS.TRIANGLES ||
                    primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP ||
                    primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN ||
                    primitive.mode === undefined) {

                    // .isSkinnedMesh isn't in glTF spec. See ._markDefs()
                    mesh = meshDef.isSkinnedMesh === true
                        ? new SkinnedMesh(geometry, material)
                        : new Mesh(geometry, material);

                    if (mesh.isSkinnedMesh === true) {

                        // normalize skin weights to fix malformed assets (see #15319)
                        mesh.normalizeSkinWeights();

                    }

                    if (primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP) {

                        mesh.geometry = toTrianglesDrawMode(mesh.geometry, TriangleStripDrawMode);

                    } else if (primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN) {

                        mesh.geometry = toTrianglesDrawMode(mesh.geometry, TriangleFanDrawMode);

                    }

                } else if (primitive.mode === WEBGL_CONSTANTS.LINES) {

                    mesh = new LineSegments(geometry, material);

                } else if (primitive.mode === WEBGL_CONSTANTS.LINE_STRIP) {

                    mesh = new Line(geometry, material);

                } else if (primitive.mode === WEBGL_CONSTANTS.LINE_LOOP) {

                    mesh = new LineLoop(geometry, material);

                } else if (primitive.mode === WEBGL_CONSTANTS.POINTS) {

                    mesh = new Points(geometry, material);

                } else {

                    throw new Error('THREE.GLTFLoader: Primitive mode unsupported: ' + primitive.mode);

                }

                if (Object.keys(mesh.geometry.morphAttributes).length > 0) {

                    updateMorphTargets(mesh, meshDef);

                }

                mesh.name = parser.createUniqueName(meshDef.name || ('mesh_' + meshIndex));

                assignExtrasToUserData(mesh, meshDef);

                if (primitive.extensions) addUnknownExtensionsToUserData(extensions, mesh, primitive);

                parser.assignFinalMaterial(mesh);

                meshes.push(mesh);

            }

            for (let i = 0, il = meshes.length; i < il; i++) {

                parser.associations.set(meshes[i], {
                    meshes: meshIndex,
                    primitives: i
                });

            }

            if (meshes.length === 1) {

                return meshes[0];

            }

            const group = new Group();

            parser.associations.set(group, { meshes: meshIndex });

            for (let i = 0, il = meshes.length; i < il; i++) {

                group.add(meshes[i]);

            }

            return group;

        });

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#cameras
     * @param {number} cameraIndex
     * @return {Promise<THREE.Camera>}
     */
    public loadCamera (cameraIndex: number): Promise<Camera> {

        let camera;
        const cameraDef = this.json.cameras[cameraIndex];
        const params = cameraDef[cameraDef.type];

        if (!params) {

            console.warn('THREE.GLTFLoader: Missing camera parameters.');
            return;

        }

        if (cameraDef.type === 'perspective') {

            camera = new PerspectiveCamera(MathUtils.radToDeg(params.yfov), params.aspectRatio || 1, params.znear || 1, params.zfar || 2e6);

        } else if (cameraDef.type === 'orthographic') {

            camera = new OrthographicCamera(- params.xmag, params.xmag, params.ymag, - params.ymag, params.znear, params.zfar);

        }

        if (cameraDef.name) camera.name = this.createUniqueName(cameraDef.name);

        assignExtrasToUserData(camera, cameraDef);

        return Promise.resolve(camera);

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#skins
     * @param {number} skinIndex
     * @return {Promise<Skeleton>}
     */
    public loadSkin (skinIndex: number): Promise<Skeleton> {

        const skinDef = this.json.skins[skinIndex];

        const pending = [];

        for (let i = 0, il = skinDef.joints.length; i < il; i++) {

            pending.push(this._loadNodeShallow(skinDef.joints[i]));

        }

        if (skinDef.inverseBindMatrices !== undefined) {

            pending.push(this.getDependency('accessor', skinDef.inverseBindMatrices));

        } else {

            pending.push(null);

        }

        return Promise.all(pending).then(function (results) {

            const inverseBindMatrices = results.pop();
            const jointNodes = results;

            // Note that bones (joint nodes) may or may not be in the
            // scene graph at this time.

            const bones = [];
            const boneInverses = [];

            for (let i = 0, il = jointNodes.length; i < il; i++) {

                const jointNode = jointNodes[i];

                if (jointNode) {

                    bones.push(jointNode);

                    const mat = new Matrix4();

                    if (inverseBindMatrices !== null) {

                        mat.fromArray(inverseBindMatrices.array, i * 16);

                    }

                    boneInverses.push(mat);

                } else {

                    console.warn('THREE.GLTFLoader: Joint "%s" could not be found.', skinDef.joints[i]);

                }

            }

            return new Skeleton(bones, boneInverses);

        });

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#animations
     * @param {number} animationIndex
     * @return {Promise<AnimationClip>}
     */
    public loadAnimation (animationIndex: number): Promise<AnimationClip> {

        const json = this.json;

        const animationDef = json.animations[animationIndex];

        const pendingNodes = [];
        const pendingInputAccessors = [];
        const pendingOutputAccessors = [];
        const pendingSamplers = [];
        const pendingTargets = [];

        for (let i = 0, il = animationDef.channels.length; i < il; i++) {

            const channel = animationDef.channels[i];
            const sampler = animationDef.samplers[channel.sampler];
            const target = channel.target;
            const name = target.node;
            const input = animationDef.parameters !== undefined ? animationDef.parameters[sampler.input] : sampler.input;
            const output = animationDef.parameters !== undefined ? animationDef.parameters[sampler.output] : sampler.output;

            pendingNodes.push(this.getDependency('node', name));
            pendingInputAccessors.push(this.getDependency('accessor', input));
            pendingOutputAccessors.push(this.getDependency('accessor', output));
            pendingSamplers.push(sampler);
            pendingTargets.push(target);

        }

        return Promise.all([

            Promise.all(pendingNodes),
            Promise.all(pendingInputAccessors),
            Promise.all(pendingOutputAccessors),
            Promise.all(pendingSamplers),
            Promise.all(pendingTargets)

        ]).then(function (dependencies) {

            const nodes = dependencies[0];
            const inputAccessors = dependencies[1];
            const outputAccessors = dependencies[2];
            const samplers = dependencies[3];
            const targets = dependencies[4];

            const tracks = [];

            for (let i = 0, il = nodes.length; i < il; i++) {

                const node = nodes[i];
                const inputAccessor = inputAccessors[i];
                const outputAccessor = outputAccessors[i];
                const sampler = samplers[i];
                const target = targets[i];

                if (node === undefined) continue;

                node.updateMatrix();

                let TypedKeyframeTrack;

                switch (PATH_PROPERTIES[target.path]) {

                    case PATH_PROPERTIES.weights:

                        TypedKeyframeTrack = NumberKeyframeTrack;
                        break;

                    case PATH_PROPERTIES.rotation:

                        TypedKeyframeTrack = QuaternionKeyframeTrack;
                        break;

                    case PATH_PROPERTIES.position:
                    case PATH_PROPERTIES.translation:
                    case PATH_PROPERTIES.scale:
                    default:

                        TypedKeyframeTrack = VectorKeyframeTrack;
                        break;

                }

                const targetName = node.name ? node.name : node.uuid;

                const interpolation = sampler.interpolation !== undefined ? INTERPOLATION[sampler.interpolation] : InterpolateLinear;

                const targetNames = [];

                if (PATH_PROPERTIES[target.path] === PATH_PROPERTIES.weights) {

                    node.traverse(function (object) {

                        if (object.morphTargetInfluences) {

                            targetNames.push(object.name ? object.name : object.uuid);

                        }

                    });

                } else {

                    targetNames.push(targetName);

                }

                let outputArray = outputAccessor.array;

                if (outputAccessor.normalized) {

                    const scale = getNormalizedComponentScale(outputArray.constructor);
                    const scaled = new Float32Array(outputArray.length);

                    for (let j = 0, jl = outputArray.length; j < jl; j++) {

                        scaled[j] = outputArray[j] * scale;

                    }

                    outputArray = scaled;

                }

                for (let j = 0, jl = targetNames.length; j < jl; j++) {

                    const track = new TypedKeyframeTrack(
                        targetNames[j] + '.' + PATH_PROPERTIES[target.path],
                        inputAccessor.array,
                        outputArray,
                        interpolation
                    );

                    // Override interpolation with custom factory method.
                    if (sampler.interpolation === 'CUBICSPLINE') {

                        track.createInterpolant = function InterpolantFactoryMethodGLTFCubicSpline (result) {

                            // A CUBICSPLINE keyframe in glTF has three output values for each input value,
                            // representing inTangent, splineVertex, and outTangent. As a result, track.getValueSize()
                            // must be divided by three to get the interpolant's sampleSize argument.

                            const interpolantType = (this instanceof QuaternionKeyframeTrack) ? GLTFCubicSplineQuaternionInterpolant : GLTFCubicSplineInterpolant;

                            return new interpolantType(this.times, this.values, this.getValueSize() / 3, result);

                        };

                        // Mark as CUBICSPLINE. `track.getInterpolation()` doesn't support custom interpolants.
                        track.createInterpolant.isInterpolantFactoryMethodGLTFCubicSpline = true;

                    }

                    tracks.push(track);

                }

            }

            const name = animationDef.name ? animationDef.name : 'animation_' + animationIndex;

            return new AnimationClip(name, undefined, tracks);

        });

    }

    public createNodeMesh (nodeIndex: number) {

        const json = this.json;
        const parser = this;
        const nodeDef = json.nodes[nodeIndex];

        if (nodeDef.mesh === undefined) return null;

        return parser.getDependency('mesh', nodeDef.mesh).then(function (mesh) {

            const node = parser._getNodeRef(parser.meshCache, nodeDef.mesh, mesh);

            // if weights are provided on the node, override weights on the mesh.
            if (nodeDef.weights !== undefined) {

                node.traverse(function (o) {

                    if (!o.isMesh) return;

                    for (let i = 0, il = nodeDef.weights.length; i < il; i++) {

                        o.morphTargetInfluences[i] = nodeDef.weights[i];

                    }

                });

            }

            return node;

        });

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#nodes-and-hierarchy
     * @param {number} nodeIndex
     * @return {Promise<Object3D>}
     */
    public loadNode (nodeIndex: number): Promise<Object3D> {

        const json = this.json;
        const parser = this;

        const nodeDef = json.nodes[nodeIndex];

        const nodePending = parser._loadNodeShallow(nodeIndex);

        const childPending = [];
        const childrenDef = nodeDef.children || [];

        for (let i = 0, il = childrenDef.length; i < il; i++) {

            childPending.push(parser.getDependency('node', childrenDef[i]));

        }

        const skeletonPending = nodeDef.skin === undefined
            ? Promise.resolve(null)
            : parser.getDependency('skin', nodeDef.skin);

        return Promise.all([
            nodePending,
            Promise.all(childPending),
            skeletonPending
        ]).then(function (results) {

            const node = results[0];
            const children = results[1];
            const skeleton = results[2];

            if (skeleton !== null) {

                // This full traverse should be fine because
                // child glTF nodes have not been added to this node yet.
                node.traverse(function (mesh) {

                    if (!mesh.isSkinnedMesh) return;

                    mesh.bind(skeleton, _identityMatrix);

                });

            }

            for (let i = 0, il = children.length; i < il; i++) {

                node.add(children[i]);

            }

            return node;

        });

    }

    // ._loadNodeShallow() parses a single node.
    // skin and child nodes are created and added in .loadNode() (no '_' prefix).
    private _loadNodeShallow (nodeIndex: number) {

        const json = this.json;
        const extensions = this.extensions;
        const parser = this;

        // This method is called from .loadNode() and .loadSkin().
        // Cache a node to avoid duplication.

        if (this.nodeCache[nodeIndex] !== undefined) {

            return this.nodeCache[nodeIndex];

        }

        const nodeDef = json.nodes[nodeIndex];

        // reserve node's name before its dependencies, so the root has the intended name.
        const nodeName = nodeDef.name ? parser.createUniqueName(nodeDef.name) : '';

        const pending = [];

        const meshPromise = parser._invokeOne(function (ext) {

            return ext.createNodeMesh && ext.createNodeMesh(nodeIndex);

        });

        if (meshPromise) {

            pending.push(meshPromise);

        }

        if (nodeDef.camera !== undefined) {

            pending.push(parser.getDependency('camera', nodeDef.camera).then(function (camera) {

                return parser._getNodeRef(parser.cameraCache, nodeDef.camera, camera);

            }));

        }

        parser._invokeAll(function (ext) {

            return ext.createNodeAttachment && ext.createNodeAttachment(nodeIndex);

        }).forEach(function (promise) {

            pending.push(promise);

        });

        this.nodeCache[nodeIndex] = Promise.all(pending).then(function (objects) {

            let node;

            // .isBone isn't in glTF spec. See ._markDefs
            if (nodeDef.isBone === true) {

                node = new Bone();

            } else if (objects.length > 1) {

                node = new Group();

            } else if (objects.length === 1) {

                node = objects[0];

            } else {

                node = new Object3D();

            }

            if (node !== objects[0]) {

                for (let i = 0, il = objects.length; i < il; i++) {

                    node.add(objects[i]);

                }

            }

            if (nodeDef.name) {

                node.userData.name = nodeDef.name;
                node.name = nodeName;

            }

            assignExtrasToUserData(node, nodeDef);

            if (nodeDef.extensions) addUnknownExtensionsToUserData(extensions, node, nodeDef);

            if (nodeDef.matrix !== undefined) {

                const matrix = new Matrix4();
                matrix.fromArray(nodeDef.matrix);
                node.applyMatrix4(matrix);

            } else {

                if (nodeDef.translation !== undefined) {

                    node.position.fromArray(nodeDef.translation);

                }

                if (nodeDef.rotation !== undefined) {

                    node.quaternion.fromArray(nodeDef.rotation);

                }

                if (nodeDef.scale !== undefined) {

                    node.scale.fromArray(nodeDef.scale);

                }

            }

            if (!parser.associations.has(node)) {

                parser.associations.set(node, {});

            }

            parser.associations.get(node).nodes = nodeIndex;

            return node;

        });

        return this.nodeCache[nodeIndex];

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#scenes
     * @param {number} sceneIndex
     * @return {Promise<Group>}
     */
    public loadScene (sceneIndex: number) {

        const extensions = this.extensions;
        const sceneDef = this.json.scenes[sceneIndex];
        const parser = this;

        // Loader returns Group, not Scene.
        // See: https://github.com/mrdoob/three.js/issues/18342#issuecomment-578981172
        const scene = new Group();
        if (sceneDef.name) scene.name = parser.createUniqueName(sceneDef.name);

        assignExtrasToUserData(scene, sceneDef);

        if (sceneDef.extensions) addUnknownExtensionsToUserData(extensions, scene, sceneDef);

        const nodeIds = sceneDef.nodes || [];

        const pending = [];

        for (let i = 0, il = nodeIds.length; i < il; i++) {

            pending.push(parser.getDependency('node', nodeIds[i]));

        }

        return Promise.all(pending).then(function (nodes) {

            for (let i = 0, il = nodes.length; i < il; i++) {

                scene.add(nodes[i]);

            }

            // Removes dangling associations, associations that reference a node that
            // didn't make it into the scene.
            const reduceAssociations = (node) => {

                const reducedAssociations = new Map();

                for (const [key, value] of parser.associations) {

                    if (key instanceof Material || key instanceof Texture) {

                        reducedAssociations.set(key, value);

                    }

                }

                node.traverse((node) => {

                    const mappings = parser.associations.get(node);

                    if (mappings != null) {

                        reducedAssociations.set(node, mappings);

                    }

                });

                return reducedAssociations;

            };

            parser.associations = reduceAssociations(scene);

            return scene;

        });

    }

}

/**
 * @param {BufferGeometry} geometry
 * @param {GLTF.Primitive} primitiveDef
 * @param {GLTFParser} parser
 */
function computeBounds (geometry, primitiveDef, parser) {

    const attributes = primitiveDef.attributes;

    const box = new Box3();

    if (attributes.POSITION !== undefined) {

        const accessor = parser.json.accessors[attributes.POSITION];

        const min = accessor.min;
        const max = accessor.max;

        // glTF requires 'min' and 'max', but VRM (which extends glTF) currently ignores that requirement.

        if (min !== undefined && max !== undefined) {

            box.set(
                new Vector3(min[0], min[1], min[2]),
                new Vector3(max[0], max[1], max[2])
            );

            if (accessor.normalized) {

                const boxScale = getNormalizedComponentScale(WEBGL_COMPONENT_TYPES[accessor.componentType]);
                box.min.multiplyScalar(boxScale);
                box.max.multiplyScalar(boxScale);

            }

        } else {

            console.warn('THREE.GLTFLoader: Missing min/max properties for accessor POSITION.');

            return;

        }

    } else {

        return;

    }

    const targets = primitiveDef.targets;

    if (targets !== undefined) {

        const maxDisplacement = new Vector3();
        const vector = new Vector3();

        for (let i = 0, il = targets.length; i < il; i++) {

            const target = targets[i];

            if (target.POSITION !== undefined) {

                const accessor = parser.json.accessors[target.POSITION];
                const min = accessor.min;
                const max = accessor.max;

                // glTF requires 'min' and 'max', but VRM (which extends glTF) currently ignores that requirement.

                if (min !== undefined && max !== undefined) {

                    // we need to get max of absolute components because target weight is [-1,1]
                    vector.setX(Math.max(Math.abs(min[0]), Math.abs(max[0])));
                    vector.setY(Math.max(Math.abs(min[1]), Math.abs(max[1])));
                    vector.setZ(Math.max(Math.abs(min[2]), Math.abs(max[2])));


                    if (accessor.normalized) {

                        const boxScale = getNormalizedComponentScale(WEBGL_COMPONENT_TYPES[accessor.componentType]);
                        vector.multiplyScalar(boxScale);

                    }

                    // Note: this assumes that the sum of all weights is at most 1. This isn't quite correct - it's more conservative
                    // to assume that each target can have a max weight of 1. However, for some use cases - notably, when morph targets
                    // are used to implement key-frame animations and as such only two are active at a time - this results in very large
                    // boxes. So for now we make a box that's sometimes a touch too small but is hopefully mostly of reasonable size.
                    maxDisplacement.max(vector);

                } else {

                    console.warn('THREE.GLTFLoader: Missing min/max properties for accessor POSITION.');

                }

            }

        }

        // As per comment above this box isn't conservative, but has a reasonable size for a very large number of morph targets.
        box.expandByVector(maxDisplacement);

    }

    geometry.boundingBox = box;

    const sphere = new Sphere();

    box.getCenter(sphere.center);
    sphere.radius = box.min.distanceTo(box.max) / 2;

    geometry.boundingSphere = sphere;

}

/**
 * @param {BufferGeometry} geometry
 * @param {GLTF.Primitive} primitiveDef
 * @param {GLTFParser} parser
 * @return {Promise<BufferGeometry>}
 */
function addPrimitiveAttributes (geometry, primitiveDef, parser) {

    const attributes = primitiveDef.attributes;

    const pending = [];

    function assignAttributeAccessor (accessorIndex, attributeName) {

        return parser.getDependency('accessor', accessorIndex)
            .then(function (accessor) {

                geometry.setAttribute(attributeName, accessor);

            });

    }

    for (const gltfAttributeName in attributes) {

        const threeAttributeName = ATTRIBUTES[gltfAttributeName] || gltfAttributeName.toLowerCase();

        // Skip attributes already provided by e.g. Draco extension.
        if (threeAttributeName in geometry.attributes) continue;

        pending.push(assignAttributeAccessor(attributes[gltfAttributeName], threeAttributeName));

    }

    if (primitiveDef.indices !== undefined && !geometry.index) {

        const accessor = parser.getDependency('accessor', primitiveDef.indices).then(function (accessor) {

            geometry.setIndex(accessor);

        });

        pending.push(accessor);

    }

    assignExtrasToUserData(geometry, primitiveDef);

    computeBounds(geometry, primitiveDef, parser);

    return Promise.all(pending).then(function () {

        return primitiveDef.targets !== undefined
            ? addMorphTargets(geometry, primitiveDef.targets, parser)
            : geometry;

    });

}
